Item I4 1.4
G BOARD OF COUNTY COMMISSIONERS
County of Monroe Mayor Sylvia Murphy,District 5
The Florida Keys l'U � � Mayor Pro Tern Danny Kolhage,District 1
�pw° Michelle Coldiron,District 2
Heather Carruthers,District 3
David Rice,District 4
County Commission Meeting
September 18, 2019
Agenda Item Number: I.4
Agenda Item Summary #5963
BULK ITEM: No DEPARTMENT: Building
TIME APPROXIMATE: STAFF CONTACT: Karl Bursa(305) 453-8759
AM
AGENDA ITEM WORDING: Approval of a resolution of the Monroe County Board of County
Commissioners adopting FEMA Technical Bulletin 8 "Corrosion Protection for Metal Connectors
and Fasteners in Coastal Areas" dated June 2019 as required pursuant to Monroe County Code
Section 122-2(c).
ITEM BACKGROUND: Chapter 122 of the Monroe County Code "Floodplain Management"
includes rules for interpreting flood hazard issues. The building official shall be guided by the
current edition of FEMA's 44 CFR, and FEMA's interpretive letters, policy statements and technical
bulletins as adopted from time to time by the board of county commissioners. FEMA's Technical
Bulletins ("bulletins") provide guidance concerning the building performance standards of the
National Flood Insurance Program (NFIP), which are contained in Title 44 of the U.S. Code of
Federal Regulations. The bulletins are intended for use primarily by State and local officials
responsible for interpreting and enforcing NFIP regulations and by members of the development
community, such as design professionals and builders. New bulletins, as well as updates to existing
bulletins, are issued periodically as needed. The bulletins do not create regulations; rather they
provide specific guidance for complying with the minimum requirements of existing NFIP
regulations. Adopting these documents as well as internal County policies would serve to allow the
County to not only remain in the NFIP as stated in Section 122-1(b), but also to maintain its standing
in FEMA's Community Rating System (CRS). The proposed resolution would adopt FEMA
Technical Bulletin 8 "Corrosion Protection for Metal Connectors and Fasteners in Coastal Areas"
dated June 2019 as required pursuant to Monroe County Code Section 122-2(c).
PREVIOUS RELEVANT BOCC ACTION:
January 18, 1994 — BOCC approved Ordinance No. 002-1994 adding the language "as adopted by
resolution from time to time by the Board of County Commissioners" to the rules for interpreting
flood hazard issues.
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July 15, 2015 — BOCC rejected proposed ordinance amending Section 122-2(c) and directed staff to
continue proposing resolutions for adoption of both new and amended documents to be used by the
building official for guidance on floodplain management.
September 16, 2015 —BOCC approved Ordinance No. 231-2015 adopting FEMA Technical Bulletin
8 "Corrosion Protection for Metal Connectors in Coastal Areas" dated August 1996 as required
pursuant to Monroe County Code Section 122-2(c).
CONTRACT/AGREEMENT CHANGES:
N/A
STAFF RECOMMENDATION: Approval
DOCUMENTATION:
FEMA_TB8_FINAL_070319_508
TB_8_Reso
FEMA Technical Bulletin Updates_BOCC.docx
FINANCIAL IMPACT:
Effective Date:
Expiration Date:
Total Dollar Value of Contract: N/A
Total Cost to County: N/A
Current Year Portion: N/A
Budgeted: N/A
Source of Funds: N/A
CPI: N/A
Indirect Costs: N/A
Estimated Ongoing Costs Not Included in above dollar amounts: N/A
Revenue Producing: N/A If yes, amount:
Grant: N/A
County Match: N/A
Insurance Required: N/A
Additional Details:
None
REVIEWED BY:
Rick Griffin Completed 08/19/2019 3:35 PM
Steve Williams Completed 08/26/2019 2:39 PM
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Assistant County Administrator Christine Hurley Completed
08/27/2019 12:49 PM
Budget and Finance Completed 08/27/2019 12:52 PM
Maria Slavik Completed 08/27/2019 1:52 PM
Kathy Peters Completed 08/28/2019 11:20 AM
Board of County Commissioners Pending 09/18/2019 9:00 AM
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Corrosion Protection
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for Metal Connectors
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and Fasteners in Coastal Areas
in Accordance with the National Flood
NFIP Technical Bulletin 8 / June 2019
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FEMA
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Comments on the Technical Bulletins should be directed to:
DHS/FEMA
Federal Insurance and Mitigation Administration (FIMA) Risk Management Directorate
Building Science Branch
400 C Street, S.W., Sixth Floor
Washington, DC 20472-3020
Technical Bulletin 8 (2019) replaces Technical Bulletin 8 (1996), Corrosion Protection for Metal Connectors
00
in Coastal Areas for Structures Located in Special Flood Hazard Areas in accordance with the National
Flood Insurance Program. 2
Cover photographs: Inset photo: Corrosion of galvanized connectors(FEMA, Fire Island, NY, after
Hurricane Sandy). Outset photo: Longer strap connectors helped maintain the connection between the
beam and floor joists(FEMA, Seaside Heights, NJ, after Hurricane Sandy)..
NFIP Technical Bulletin 8 contains information that is proprietary to and copyrighted by the American
Society of Civil Engineers and information that is proprietary to and copyrighted by the International Code
Council, Inc. All information is used with permission.
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For more information, see the FEMA Building Science
Frequently Asked Questions website at http://wwwJema.gov/ To order publications, contact the FEMA �
frequently-asked-questions-buildinq-science. Distribution Center: i
Call: 1-800-480-2520
If you have any additional questions on FEMA Building (Monday-Friday, 8 a.m.-5 p.m., EST)
Science Publications, contact the helpline at FEMA- Fax: 719-948-9724 00 1
Buildingsciencehelp@fema.dhs.gov or 866-927-2104. Email: FEMAr)ubs@qr)g.gov
You may also sign up for the FEMA Building Science email Additional FEMA documents can be
subscription, which is updated with publication releases found in the FEMA Library at
and FEMA Building Science activities. Subscribe at htt s:// htlps://www.fema.gov/media-library/
service.govdeliverv.com/accounts/USDHSFEMA/subscriber/ �
resources.
new?top c_id=USDHSFEMA_193.
Please scan this QR code
Visit the Building Science Branch of the Risk Management to visit the FEMA Building �•
Directorate at FEMA's Federal Insurance and Mitigation Science web page.
Administration at https://www.fema.gov/building-science. •❑,
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Table of Contents
Acronyms.......................................................................................................................................................iii
1 Introduction .....................................................................................................................................................1
2 NF P Regulations.............................................................................................................................................1
Other Regulations 3
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3.1 International Residential Code.............................................................................................................3
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3.2 International Building Code and ASCE 24..........................................................................................4
Importance of Selecting Proper Connectors and Fasteners for a Continuous Load Path...............................6
Light Gauge Metal Connectors and Corrosion 8
5.1 Known Concerns Related to Nominally Galvanized Metal Connectors ............................................9 0
5.2 Metal Connector and Fastener Materials and Fabrication................................................................11
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Causes of Corrosion in Coastal Areas 13
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6.1 Salt Spray from Breaking Waves and Onshore Winds.......................................................................13
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6.2 Distance from Ocean 13
...........................................................................................................................
6.3 Elevation Above Ground......................................................................................................................14
6.4 Exposure to Corrosion and Building Orientation.............................................................................14
6.5 Weather and Rates of Corrosion.........................................................................................................14 ®�
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6.6 Identifying Areas with Increased Corrosion Rates............................................................................15
7 Exposure Classes for Connectors and Fasteners..........................................................................................15
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7.1 Partially Sheltered Exterior Exposure 16 4i
7.2 Open Exposed Exterior Exposure......................................................................................................16
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7.3 Vented Enclosed Exposures.................................................................................................................16
7.4 Unvented Enclosed Exposures............................................................................................................17
7.5 Interior Living Space Exposures.........................................................................................................17
6 Improving Corrosion-Resistant Materials and Coatings................................................................................17
8.1 Thicker Galvanizing.............................................................................................................................19
8.2 Stainless Steel.......................................................................................................................................20
8.3 Applied Coatings and Paint.................................................................................................................20
FIP TECHNICAL BULLETIN 8 JUNE 2019
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8.4 Other Corrosion-Resistant Fasteners..................................................................................................21
9 Guidance for Connector and Fastener Corrosion Control..............................................................................21
9.1 Reducing Corrosion Rates...................................................................................................................22
9.2 Maintenance and Replacement Considerations.................................................................................24
10 Summary of Best Practices for Corrosion Resistance ..................................................................................26
11 References and Resources............................................................................................................................29
11.1 References.............................................................................................................................................29
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11.2 Resources..............................................................................................................................................31
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List of Figures
Figure 1: Example of using metal connectors and fasteners to create a continuous load path.................7
Figure 2. Common wind anchor and metal truss plate 8
Figure 3. Common single-and double-joist hangers 8
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Figure 4: Wood product identification tag...................................................................................................10
Figure 5: Variation in the corrosion rate of steel with elevation at two distances from the ocean
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for Kure Beach, NC La ue 1975 14
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Figure 6: Corrosion exposure classes and their locations...........................................................................15 Q
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Figure 7: Galvanic chart of common metals................................................................................................18
Figure 8: Approximate service life improvement from increasing galvanization thickness.....................19 �-
Figure 9: Traditional wooden ledger boards used in place of joist hangers in high corrosion areas......23
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Figure 11: Wooden wind anchors used to connect floor joists to floor beams............................................23
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Figure 10: Detail of an elevated floor-to-beam connection using wood uplift blocking and
full-depth solid blocking...............................................................................................................23
Figure 12: Zinc galvanizing on connectors that has corroded.....................................................................25
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List of Tables
Table 1: Comparison of Select 2018 IRC and NFIP Requirements.............................................................3 0
Table 2: Comparison of Select 2018 IBC and ASCE 24-14 Requirements with NFIP Requirements .......4 <
Table 3: Recommendations on Corrosion-Resistant Materials and Methods..........................................27
ii NFIP TECHNICAL BULLETIN
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Acronyms
ANSI American National Standards Institute
ASCE American Society of Civil Engineers
ASTM ASTM International
AWC American Wood Council
BFE base flood elevation
CCA chromated copper arsenate
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CFR Code of Federal Regulations S
DHS Department of Homeland Security
FEMA Federal Emergency Management Agency
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FIRM Federal Insurance Rate Map ca
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IBC International Building Code®
ICC International Code Council® LU
ICC-ES ICC Evaluation Service 00
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I-Codes International Codes® C)I
IMOA International Molybdenum Association
IRC International Residential Code®
NDS National Design Specification
NFIP National Flood Insurance Program 00
oz/ft2 ounces per square foot
PWF Permanent Wood Foundation LU
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SEI Structural Engineering Institute
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SFHA Special Flood Hazard Area
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SSPC Society for Protective Coatings
TPI Truss Plate Institute
NFIP TECHNICAL BULLETIN 8 JUNE 2019
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1 Introduction
This Technical Bulletin explains the importance of
using corrosion-resistant metal connectors and fasteners NFIP TECHNICAL BULLETIN 0
in the construction of coastal structures, areas using NFIP Technical Bulletin 0, User's Guide
preservative-treated lumber, and any locations subject to to Technical Bulletins, should be used
contact with floodwater or windblown rain. as a reference in conjunction with this
Post-disaster assessments of wood-framed buildings Technical Bulletin. Technical Bulletin 0
following natural hazard events such as high winds, describes the purpose and use of the
floods, and earthquakes have revealed that structural Technical Bulletins, includes common
failures frequently occur at connections rather than concepts and terms, lists useful 00
in framing members. In coastal areas, where higher
resources, and includes a crosswalk
of the sections of the NFIP regulations _
moisture and humidity levels exist and buildings are identifying the Technical Bulletin
exposed to salt spray, corroded metal connectors and that addresses each section of the
fasteners have been observed to contribute to the loss of regulations and a subject index. .2
an adequate load path.The loss of an adequate load path
often results in damage to or failure of the structure. Readers are cautioned that the definition
This Technical Bulletin presents guidance on addressing of some of the terms that are used in <
and avoiding the corrosion of connectors and fasteners. the Technical Bulletins are not the same W
when used by the NFIP for the purpose
Questions pertaining to minimizing or avoiding of rating flood insurance policies. 00
corrosion of connectors and fasteners should be directed `O�
to the appropriate product manufacturers, local official,
NFIP State Coordinating Office, or the Federal Emergency Management Agency (FEMA) Regional Office. �.
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2 NFIP Regulations
An important National Flood Insurance Program
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NFIP objective is protecting buildings constructed
(NFIP) J p g g I-CODES AND ASCB
in Special Flood Hazard Areas (SFHAs) from damage
caused by flood forces. The SFHA, composed of Zones The International Codes (I-Codes)and E
the standard, ASCE 24, Flood Resistant o
A and V, is the areal extent of the base flood shown Design and Construction, include
on Flood Insurance Rate Maps (FIRMs) prepared by requirements for metal connectors and
FEMA. The base flood is the flood that has a 1 percent fasteners used in coastal areas that
chance of being equaled or exceeded in any given year are susceptible to salt spray to address
(commonly called the "100-year flood"). metal corrosion.
The NFIP regulations are codified in Title 44 of the
Code of Federal Regulations (CFR) Part 60. Specific to
this Technical Bulletin, in coastal regions, corrosion-resistant connectors and fasteners are essential to
maintaining a building's load paths and demonstrating compliance with 44 CFR Sections 60.3(a)(3) and
60.3(e)(4).
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Section 60.3(a)(3) is applicable to all SFHAs:
If a proposed building site is in a flood-prone area, all new construction and substantial
improvements shall (i) be designed (or modified) and adequately anchored to prevent
flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and
hydrostatic loads,including the effects of buoyancy, (ii) be constructed with materials resistant
to flood damage, (iii) be constructed by methods and practices that minimize flood damages
Section 60.3(e)(4) is applicable to Coastal High Hazard Areas (Zone V):
... new construction and substantial improvements... [shall be] elevated on pilings and
columns so that ...(ii) the pile or column foundation and structure attached thereto is 'a
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anchored to resist flotation, collapse and lateral movement due to the effects of wind and water M
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loads acting simultaneously on all building components. Water loading values used shall be S
those associated with the base flood. Wind loading values used shall be those required by
applicable State or local building standards.
.2
NFIP REQUIREMENTS AND HIGHERG L,A7 Y STANDARDS �
State and Local Requirements. State or local requirements that are more stringent than the minimum
requirements of the NFIP take precedence. The Technical Bulletins and other FEMA publications provide LU
guidance on the minimum requirements of the NFIP and describe best practices. Design professionals,
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builders, and property owners should contact local officials to determine whether more restrictive CD
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provisions apply to buildings or sites in question. All other applicable requirements of the State or local i
building codes must also be met for buildings in flood hazard areas.
Substantial Improvement and Substantial Damage.As part of issuing permits, local officials must i
review not only proposals for new construction but also for work on existing buildings to determine
whether the work constitutes Substantial Improvement or repair of Substantial Damage. If the work is
determined to constitute Substantial Improvement or repair of Substantial Damage, the buildings must i
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be brought into compliance with NFIP requirements for new construction. Some communities modify the
definitions of Substantial Improvements and/or Substantial Damage to be more restrictive than the NFIP
minimum requirements.
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For more information on Substantial Improvement and Substantial Damage, see FEMA P-758, Substantial
Improvement/Substantial Damage Desk Reference (2010b), and FEMA 213,Answers to Questions About
Substantially Improved/Substantially Damaged Buildings (2018a).
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Flood Damage-Resistant Materials. Guidance on the NFIP requirement regarding the use of building
materials resistant to flood damage can be found in Technical Bulletin 2, Flood Damage-Resistant
Materials Requirements.
2 NFIP TECHNICAL BULLETIN
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3 Other Regulations
In addition to complying with NFIP requirements, all new construction, Substantial Improvements, and
repair of Substantial Damage must comply with applicable building codes and standards that have been
adopted by States and communities.
The International Codes® (I-Codes®), published by the International Code Council® (ICC®) are a family
of codes that includes the International Residential Code® (IRC®), International Building Code® (IBC®),
International Existing Building Code® (IEBC®), and codes that govern the installation of mechanical,
plumbing, fuel gas service, and other aspects of building construction. FEMA has deemed that the
latest published editions of the I-Codes meet or exceed NFIP requirements for buildings and structures. 0
Excerpts of the flood provisions of the I-Codes are available on FEMAs Building Code Resource webpage 00
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3.1 International Residential Code
The IRC applies to one-and two-family dwellings and townhomes not more than three stories above grade M
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plane,with certain limitations for high wind, high seismic, and high snow regions. The IRC requirements
that are related to connectors and fasteners in coastal areas are summarized in Table 1. Q
Although Table 1 refers to selected requirements of the 2018 IRC and notes changes from the 2015 and .�
2012 editions, subsequent editions should include comparable requirements. 00
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Table 1:Comparison of Select 2018 IRC and NFIP Requirements
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Fasteners and Section R317.3.1 Fasteners for preservative-treated wood. No NFIP requirement
connectors Requires all fasteners used for pressure-treated wood to be corrosion
resistant. Specific requirements for connectors are outlined in the IRC. 00
The coating type and weights of connectors shall either be as specified by
the manufacturer or meet the minimum requirements as specified in the
IRC. Exceptions to this requirement are outlined in the IRC.
Change from 2015 to 2018 IRC: The need for staples to be stainless steel
was added.
Change from 2012 to 2015 IRC: No changes.
Flood-resistant Section R322.1.2 Structural systems. Equivalent to NFIP
construction Requires that buildings and structures be designed and constructed to regulation in 44 CFR
resist flood forces during a design flood event.This includes connecting §§60.3(a)(3)(i)and
structural systems and anchoring the building to resist flotation, collapse (iii),and§60.3(e)(4)
or permanent lateral movement during a design flood.
Changes from 2015 to 2018 IRC: No change.
Changes from 2012 to 2015 IRC: No change.
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Table 1:Comparison of Select 2018 IRC and NFIP Requirements(concluded)
EMENSiMSEEMEMEMEEM
Flood damage- Section R322.1.8 Flood-resistant materials. Equivalent to NFIP
resistant Requires materials used below the required design flood elevation to be regulation in 44 CFR
materials flood damage resistant in conformance with NFIP Technical Bulletin 2. §60.3(a)(3)(ii)
Change from 2015 to 2018 IRC: No change.
Change from 2012 to 2015 IRC: The need for wood to be pressure-treated,
preservative-treated, or decay-resistant heartwood was deleted to clarify
that the guidance in NFIP Technical Bulletin 2 is adequate to meet flood
damage-resistant material requirements.
Used with permission from ICC.
3.2 International Building
The flood provisions in the latest published editions of the
IBC meet or exceed the NFIP requirements for buildings IBC AND ASCE COMMENTARIES
largely through reference to the standard ASCE 24, Flood
Resistant Design and Construction, developed by the American ICC publishes companion
Society of Civil Engineers (ASCE). The IBC applies to all commentary for the IBC and ASCEpublishes companion commentary
applicable buildings and structures. While primarily used for ASCE 24. Although not
for buildings and structures other than dwellings within the
regulatory, the commentaries provide
scope of the IRC, the IBC may be used to design dwellings. information and guidance that are Q
The IBC and ASCE 24 requirements related to the use of useful in complying with, interpreting, rrsl
corrosion-resistant fasteners (often used for maintaining a and enforcing requirements.
building load path), which are summarized in Table 2, are
more specific than NFIP regulations and also apply to areas
where the minimum elevation requirements are above the base flood elevation (BFE) by the incorporation
of freeboard.
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Although Table 2 refers to selected requirements of the 2018 IBC and ASCE 24-14 (noting changes from
2015 and 2012 IBC and ASCE 24-05), subsequent editions should include comparable requirements. �I
Table 2:Comparison of Select 2018 IBC and ASCE 24-14 Requirements with NFIP Requirements ILL
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General design 2018 IBC, Section 1612.2 Design and construction. For Zones A and V,
requirement Requires buildings and structures located in all delineated flood hazard equivalent to NFIP
areas to be designed and constructed in accordance with Chapter 5 of 44 CFR§60.3
ASCE 7 (Minimum Design Loads and Associated Criteria for Buildings and For Coastal A Zones,
Other Structures)and ASCE 24. more restrictive than
Change from 2015 to 2018 IBC: Section renumber from 1612.4 to 1612.2. the NFIP since the
Change from 2012 to 2015 IBC: Applies to coastal high hazard area NFIP does not define
requirements in Coastal A Zones, if delineated. Coastal A Zones
4 NFIP TECHNICAL BULLETIN 8
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Table 2:Comparison of Select 2018 IBC and ASCE 24-14 Requirements with NFIP Requirements(continued)
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Fasteners and 2018 IBC, Section 2304.10.5 Fasteners and connectors in contact No NFIP requirement
connectors for with preservative-treated and fire-retardant-treated wood.
preservative- Requires all fasteners used for pressure-treated and fire-retardant-treated
treated wood wood to be corrosion resistant and shall be compliant with Sections
2004.10.5.1 through 2304.10.5.4. Coating requirements for zinc coatings
and stainless steel fasteners are specified in the IBC.
Fasteners and 2018 IBC, 2304.10.5.1 Fasteners and connectors for preservative- No NFIP requirement
connectors for treated wood.
preservative- Requires all fasteners used for pressure-treated wood to be corrosion
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treated wood resistant. Specific requirements for connectors are outlined in the IBC.
(cont.) The coating type and weights of connectors shall either be as specified by 00
the manufacturer or meet the minimum requirements as specified in the
IBC.An exception for carbon steel fasteners is outlined in the IBC.
2018 IBC, 2304.10.5.2 Fastenings for wood foundations.
Requires all fasteners used for wood foundations to be compliant with
the American Wood Council's Permanent Wood Foundation Design
Specification with Commentary, 2015 Edition (ANSI/AWC PWF-2015 M
[2014b]).
2018 IBC,2304.10.5.3 Fasteners for fire-retardant-treated wood used
in exterior applications or wet or damp locations.
Requires all fasteners used for fire-retardant-treated wood in exterior
applications or wet or damp locations to be corrosion resistant. Specific 00
requirements for fasteners are outlined in the IBC. LO
2018 IBC,2304.10.5.4 Fasteners for fire-retardant-treated wood used
in interior applications.
Requires all fasteners used for fire-retardant-treated wood in interior
locations to be as specified by the manufacturer, or if those specifications
do not exist,the fasteners meet the requirements of Section 2304.9.5.3.
Changes from 2015 to 2018 IBC: Standards for driven fasteners and the LL
need for staples to be stainless steel were added. 00
Changes from 2012 to 2015 IBC: Section 2304.9.5 was renumbered to
2304.10.5.
Flood damage- ASCE 24-14,Section 5.1 General Equivalent to NFIP
resistant Requires that, in flood hazard areas, all materials used in new construction 44 CFR§60.3(a)(3) .i
materials and substantial improvaements be constructed of flood damage-resistant with more specificity
materials below the required elevations specified in Table 5-1 of ASCE on requirements
24-14. Also requires materials to be of sufficient strength, rigidity, and for connectors and M
durability to adequately resist all flood-related and other loads or to be fasteners
designed as breakaway or as otherwise permitted in the standard.
Change from ASCE 24-05: Duplicative statement at the end of the section
on the need for materials to have sufficient strength, rigidity, and durability
to resist flood loads was removed.
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Table 2:Comparison of Select 2018 IBC and ASCE 24-14 Requirements with NFIP Requirements(concluded)
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Metal ASCE 24-14,Section 5.2.1 Metal Connectors and Fasteners No NFIP requirement
connectors and Requires that metal connectors and fasteners exposed to floodwater,
fasteners precipitation, or wind-driven water meet specific standards as outlined in
ASCE 24-14 for corrosion resistance.
Change from ASCE 24-05: Updated references to materials standards.
ASCE 24-14,Section 5.2.2.1 Corrosive Environments
Requires structural steel exposed to saltwater, salt spray, or other
corrosive materials be hot-dipped galvanized after fabrication and other
secondary components to meet the requirements of Section 5.2.1.
Change from ASCE 24-05: No change.
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Used with permission from ICC and ASCE.
4
2 Importance of Selecting
.
Connectors and Fasteners
for a Continuous Load Path
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Buildings are exposed to numerous forces (loads), including those associated with wind events, floods,
snow accumulation, and earthquakes. For a building to survive exposure to such forces, loads must be
transferred through the building's structure to the soils that support the building along what are typically
referred to as load paths. Load paths consist of structural elements (e.g., beams, columns, bearing walls)
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and the components that connect these elements. In light-frame construction, structural elements are 000
often connected with metal connectors and fasteners (fasteners include screws,bolts, and nails).Examples
are shown in Figure 1. I
Metal connectors are premanufactured components that are usually cut from flat steel sheets and formed
into a shape to efficiently transfer loads from one structural element to another. The load capacities of
metal connectors, often determined by the manufacturer through testing or analysis, are published for E
use by design professionals and contractors to meet the load requirements for their project.
Metal connectors and fasteners are important elements in transferring loads from natural hazards (e.g.,
flood, wind, seismic) through a building. Corrosion rates for metal are dramatically higher in coastal
environments than in less harsh, non-coastal environments. Therefore, it is important to increase the
corrosion protection for metal connectors and fasteners in coastal environments. See Section 6 for
information on the causes of corrosion in coastal areas. Studies have shown that stainless steel and
thick hot-dip galvanized (G185 or higher) metal connectors and fasteners improve corrosion protection.
Selecting metal connectors and fasteners made of the same metal and either hot-dip galvanized or
stainless steel will improve performance. See Section 8 for information on improving corrosion resistance.
6 NFIP TECHNICAL BULLETIN
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Regardless of the metal that is selected, routine inspection is important to identify when replacement is
necessary. See Section 9.2 for information on inspections.
Preservative-treated lumber, which is commonly used in many buildings, requires special attention when
selecting connectors and fasteners. See Section 5.1.1.
Vertical uplift component
a. Wind uplift
pressure Roof diaphragm
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b. A
Vertical b•
' load path A Braced wall panel LU
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pressure
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load path
The foundation �Main floor �
transfers all beams as
building loads E
to the ground 'o ca
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Figure 1: Example of using metal connectors and fasteners to create a continuous load path
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5 Light Gauge Metal Connectors
and Corrosion
The term "light gauge metal connectors" is used in this Technical Bulletin to highlight the importance
of corrosion protection for lighter gauge connectors such as the prefabricated connectors that are used
to facilitate wood connections. However, metal connectors fabricated from thicker steel will also benefit
from this guidance.
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Light gauge metal connectors are commonly used in several locations throughout wood-framed buildings. 'a
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Concrete and masonry structures may also use them. Although light gauge metal connectors are not M
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unique to wood-framed buildings, this Technical Bulletin highlights aspects of using them in wood- r_
framed buildings in areas where corrosion can occur.
Light gauge metal connectors are often used to create a load path by securing roof framing to the tops of
load-bearing walls, connecting walls of upper floors to lower floors, and connecting walls to foundations. 0
The selection of the type of metal connector to use for specific applications may be dictated by the
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building code or may be based on the relative ease a type of connector offers in making complex framing
connections. Metal connectors such as wind anchors may be used instead of toe-nailed connections to
increase the strength of connections of a roof truss to a top plate (see Figure 2). In some cases, such LU
as when attaching floor joists to floor band joists, metal connectors can both improve the connection LL
and also reduce labor costs see Figure 3 In some portions of a building's load path, light gauge metal Q
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connectors can make the connection several times stronger than a connection that is readily achievable �I
by nails alone.
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Metal connector Top chord Double
wind anchor of truss joist
hanger
Double 00
Wood truss floor band
0
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LL
0
0
a Bottom chord /j 0
00 00
a oo_m000 of truss
om�oo� E
m000�� Double 01,
Metal truss plate joist 0
Floor
joist
Joist
hanger
Wall stud
Figure 2: Common wind anchor and metal truss plate Figure 3: Common single-and double-joist hangers
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Despite the benefit of being stronger than nails alone, light gauge metal connectors have drawbacks
in coastal environments. Metal connectors that are prone to corrosion can lead to load path failures
and structural damage during natural hazard events. The following are examples of important metal
connectors potentially subject to corrosion:
• Hurricane straps and wind anchors used to connect roofs to walls (see Figure 2)
• Truss plates that connect the members of pre-manufactured roof and floor framing systems
• Joist hangers used on floor joists (see Figure 3), beams, and rafters
• Other metal connectors such as those used to improve lateral load resistance
0
5.1 Known Concerns RelatedNominally I i I Connectors M
00
In this Technical Bulletin, the term "nominally galvanized metal connectors" refers to connectors that
as
have the minimum galvanization provided by the manufacturer and that do not have corrosion resistance
beyond the minimum.
Nominally galvanized metal connectors should be upgraded when enhanced corrosion resistance or .2
greater strength in the connection is needed or desired.
.1.1 Chemicals in Preservative-Treated o0
LU
Salt spray in coastal environments and the chemicals in the preservatives that are used to treat wood can ._
both contribute to the corrosion of metal fasteners. One of the chemicals in preservatives, chromated Q
copper arsenate (CCA), was removed in 2004 from formulations for preservative-treated wood for most
building applications. Several formulations to replace CCA were developed, including some that are
more chemically reactive and therefore more corrosive to metal connectors and fasteners. As a result,
manufacturers of several of the new formulations specified that all fasteners used with preservative-treated _I
framing be stainless steel or hot-dip galvanized metal with a defined minimum amount of galvanizing.
Which chemical is used in the treatment and the amount of chemical in the wood after treatment, referred 001
co
to as retention, can both influence the corrosion rate.Wood treated for use in more severe environments,
such as in direct contact with the ground, has higher chemical retention than wood treated for use in less
severe environments. Higher retention can increase the corrosion rate. Connector manufacturers may LU
have recommendations on selecting connectors and fasteners that will be in contact with treated wood.
Lumber manufacturers attach identification tags to treated wood products to indicate the type of
preservative that was used (see Figure 4). The tags allow designers and builders to select connectors and
fasteners that are compatible with the amount and type of preservative in the wood and its intended
environment.
5.1.2 Galvanic Corrosion
Galvanic corrosion is the corrosion that results when two metals with different electrical potential are in
contact with each other and are in the presence of an electrolyte such as saltwater. Galvanic corrosion is
an electrochemical process in which one of the metals corrodes and the other one is protected.
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Metals can be protected from galvanic corrosion by applying a sacrificial metal to a metal surface (see
Section 8). The metals involved in galvanic corrosion can be (1) the metallic compounds in wood
preservatives and the metal connectors the compounds are in contact with or (2) metal connectors
and adjoining fasteners if they are made of dissimilar metals such as stainless steel and aluminum. It is
important that fasteners and connectors be made of similar metals to prevent galvanic corrosion. Galvanic corrosion
can occur anywhere but can occur more quickly in coastal environments.
9
BUILDING CODE COMPLIANT—LIFETIME LIMITED WARRANTY ag
PRESSURE TREATED USING
MICRONIZED COPPER AZOLE COMPOUNDS 91
0.15 pcf
Treated:5/4x6x10'PREMIUM WS 00
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Limited Lifetime Warranty ®I
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Preservative-treated wood is commonly referred to as"pressure treated" lumber and has
LU
an identification tag attached to the lumber.The tag contains the following information: LL
1 Identification of treating manufacturer
2 Type of preservative
3 Minimum preservative retention(pcf)
End use for which the product is treated
5 Standard to which the product was treated or ICC-ES Evaluation Report Number
6 Identity of the approved inspection agency
7 Size, Length, Grade, Species(Optional)
Figure 4:Wood product identification tag
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5.2 Metal Connector and Fastener MaterialsFabrication
Most light gauge metal connectors are made from thin,
flat sheets of steel that has been galvanized (has a zinc CORROSION OF BRICK TIES
coating that was applied during fabrication). In flat sheet Metal brick ties and their fasteners are
form, steel is sufficiently strong for connectors and is also subject to corrosion. Fact Sheet 5.4,
readily workable and relatively inexpensive, all of which "Attachment of Brick Veneer in High-
make it well suited for connectors. Most fasteners (e.g., Wind Regions" in FEMA P-499, Home
screws, bolts, nails) are also made of steel. Builder's Guide to Coastal Construction
(2010a), contains recommendations on
Unprotected (ungalvanized) steel is subject to corrosion,
improving the attachment of brick veneers
even in inland areas, and corrodes rapidly in salt air. 'a
to buildings. The recommendations in this CL
To protect against corrosion, most light gauge metal Technical Bulletin for corrosion-resistant M
connectors and fasteners are galvanized. connectors and fasteners also apply to
the proper selection of corrosion-resistant 2
.2.1 Galvanizing brick ties and fasteners.
Galvanizing is the process of coating steel with zinc.
a�
In hot-dip galvanizing, the steel is carefully cleaned and then dipped into a vat of molten zinc. The high 0
temperature melts the surface of the steel and forms several steel/zinc alloys that tightly bond the zinc
coating to the steel base metal; various thicknesses of zinc coatings are achievable. The protective zinc
coating still corrodes, but the corrosion of the zinc protects the steel base metal. Galvanized steel can w
degrade up to more than 50 times slower than ungalvanized steel in the same coastal environment. 00
Q
eO
Zinc can also be applied mechanically. The method MI
typically involves tumbling the metal parts in acid and HOT-DIP GALVANIZING COATING
copper to mechanically weld a zinc coating onto a steel DESIGNATION SYSTEM
surface. This method is preferred for applying zinc ASTM A653(2015a) uses a coating
to threaded parts, such as machine screws, because it designation for hot-dip galvanizing that
creates a uniform thickness of the coating. As with hot- indicates the amount of galvanizing in M
ounces per square foot oz/ft2 of surface 00
dip galvanizing, various thicknesses of zinc coatings are p Q ( ) 00
achievable. area. For example, hardware designated
as G185 has a galvanized coating that
Mechanically galvanized fasteners are appropriate for weighs 1.85 oz/ft2 (the weight includes LL
some applications, but mechanically applied galvanized both surfaces of the coated material)
coatings are typically thinner and more brittle than hot- and a minimum of 0.64 oz/ft2 on one
dip galvanized coatings, so mechanically galvanized side because coatings are not always
fasteners are discouraged for exterior applications, evenly distributed on both sides. Metal
particularly in coastal environments. The IBC and IRC connectors are often stamped with
prohibit mechanical galvanizing for driven fasteners such the coating designation, but fasteners
as nails and timber rivets because mechanically galvanized generally are not, so it is necessary to look
coatings may deteriorate during installation. For these at the packaging to determine the amount
applications, hot-dip galvanized coated steel or stainless of galvanizing for fasteners.
steel fasteners are recommended.
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.2.2 Protective Properties of Zinc
Galvanizing is particularly effective for steel because,unlike most other coatings, zinc sacrificially protects
bare steel edges and scratches. The zinc surface near a scratch corrodes slightly faster than the zinc
surrounding it and fills small scratches with zinc corrosion products, preventing the steel from rusting
until the nearby zinc is consumed. The protection of bare edges and scratches offered by galvanizing is
important because many connectors are fabricated after the steel sheet metal has been galvanized, and
fabrication can remove the zinc and expose the base metal.
Zinc also differs from other coatings (or paints) and most metals by corroding at a relatively steady rate
in most atmospheric exposures. Therefore, doubling the thickness of the zinc coating approximately
doubles the protection period. 'a
CL
5.2.3 Standards and Codes 00
ASTM International (ASTM) has established national standards for galvanizing that are referenced by
the I Codes,ASCE 24, and most local building codes. The standards are contained in the following: co
• Hot-dip galvanized steel sheets used in the manufacture of metal connectors are covered in ASTM 2
a�
A653, Standard Specification for Steel Sheet, Zinc-Coated(Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed)
by the Hot-Dip Process (2015a).
• Metal connectors that are hot-dip galvanized after fabrication are covered in ASTM A153/A153M,
Standard Specification for Zinc Coating(Hot-Dip) on Iron and Steel Hardware (2016).
00
• Hot-dip galvanizing of most fasteners is covered by ASTM A123, Standard Specification for Zinc (Hot-Dip LO
Galvanized) Coatings on Iron and Steel Products (2015b).
• Mechanically applied galvanizing is covered in ASTM B695-04, Standard Specification for Coatings of �.
Zinc Mechanically Deposited on Iron and Steel (2004),which states that Class 55 is the minimum thickness
allowed to be in contact with preservative-treated lumber. z
M
The I-Codes require that treated wood or the connector manufacturer's recommendations be followed 0�
when connectors are in contact with preservative-treated lumber. In the absence of direction, the I-Codes
require that a minimum G185 zinc-coated steel be used (some exceptions are provided). Use of Type 304
or Type 316 stainless steel is regarded as exceeding the minimum G185 zinc-coated steel code requirement W
LL
for corrosion protection. Stainless steel types are explained in Section 8.2 of this Technical Bulletin.
5.2.4 Proprietary oati s
For some types of fasteners, particularly screws, manufacturers use a proprietary coating rather than
simple galvanization. One advantage of using a proprietary coating is that the coating can be more
uniform to allow the threads to function normally. Manufacturers may have a building code evaluation
report to show that their coating is equivalent to one of the prescriptive corrosion-resistant coatings
required by the codes.
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6 Causes of Corrosion in Coastal Areas
Corrosion of metal fasteners and connectors is accelerated
when a certain level of surface wetness is exceeded, EXPOSURE CLASS
initiating electrochemical reactions among the metal, As used in this Technical Bulletin, the
salts, and air. The conditions that accelerate the rate term "exposure class" relates to areas of
of corrosion near the coast have been studied at a few buildings exposed to different conditions
field stations and in research laboratories. The studies that affect corrosion. It is different from
identified the major factors that contribute to accelerated the term "Exposure Category," which is
corrosion rates as including proximity to the shoreline, used in the wind load requirements of the 'a
CL
high temperature,high humidity, elevation, exposure class I-Codes. M
00
(see text box) including sheltering, and certain airborne Exposure classes are outlined in Section 7
pollutants.While it may be infeasible to determine the rate of this Technical Bulletin, 2
of corrosion at specific sites, it is helpful to understand the
factors that contribute to corrosion so that appropriate
design, construction, and maintenance activities can be implemented.
ca
6.1 SaltiWinds
LU
Salt spray from breaking waves and onshore winds significantly accelerates the rate of corrosion of metal
connectors and fasteners. Ocean salts, which are primarily sodium chloride but include other chlorides 00
and compounds, accumulate on metal surfaces and accelerate the electrochemical reactions that cause LO
rusting and other forms of corrosion. The combination of salt accumulation on the surface and the high
humidity common in many coastal areas further accelerates the corrosion rate of untreated steel and
other metals commonly used in connectors, fasteners, and other building materials. The longer a surface
remains damp during the normal daily fluctuations in humidity, the higher the corrosion rate. Onshore
winds carry both salt and moisture inland from the ocean. Therefore, corrosion rates are higher along
shorelines with predominantly onshore winds than along shorelines with predominantly offshore winds. 00
6.2 Distance
LU
When waves break, salt water is aerosolized, and the wind tends to distribute the salt spray to inland areas.
The amount of salt spray in the air is greatest near breaking waves and declines rapidly in the first 300 E
to 3,000 feet landward of the shoreline. Despite the inland reduction, studies have shown accelerated ca
corrosion rates as far inland as 5 to 10 miles (IMOA, 2009). Farther landward, corrosion can be similar to
the rates that occur in milder, inland conditions.
Although the width of high-corrosion areas varies along the shoreline, it is appropriate to assume that
oceanfront and nearshore buildings can be more severely affected than buildings farther inland. Tests in
North Carolina in the 1940s found that samples of iron corroded 10 times faster 80 feet landward of the
shoreline than samples of the same material 800 feet landward of the shoreline (Lague, 1975). Similar
results have been noted around the world.
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6.3 Elevation
Corrosion Rate Variation with Elevation
Lague (1975) determined that elevation 35
above the ground, in addition to distance
from the ocean, affected rates of corrosion 30
in tests at Kure Beach, NC. The tests showed
that the rate of corrosion reached a peak at 25
approximately 12 feet above the ground near 800 ft 80 ft from ocean
the shoreline (see Figure 5), approximately 0 20 from
equal to the lowest floor elevation of an ocean
elevated building with parking underneath. 15
In several rows of buildings farther inland, o _ Peak corrosion rate___
the corrosion rate was found to be lower, but 10 00
the rate was highest at an elevation above w
the roofs of small buildings. The tests also 5 - 5,0 0
0
indicated that the highest corrosion rate near
the ocean was more than twice the corrosion 0 2
rate farther inland. 0 10 20 30
Corrosion Rate(mils/yr)
6.4 Exposure to CorrosionFigure 5:Variation in the corrosion rate of steel with elevation at
and
I I I rl I two distances from the ocean for Kure Beach, NC(Lague, 1975) LU.0
00
CD
Both exposure and building orientation affect corrosion rates (exposure classes are described in Section 7 LO
of this Technical Bulletin). Exposed areas such as building exteriors are often coated with large amounts
of salt spray and can be expected to suffer high corrosion rates. Lague (1975) found that the metals on
the side of a building facing the ocean corrode much faster than those facing away from the ocean.
Perhaps less obvious is LaQue's finding that partially sheltered exposures, such as areas under piling-
supported buildings or under decks and walkways, can experience even greater corrosion than open ®-
00
exposures. Tests showed that portions of buildings exposed to rain may undergo lower corrosion rates
than sheltered areas because rain can periodically wash away salt accumulations. Sheltered or covered
areas, on the other hand, do not benefit from occasional rinsing from rain and therefore accumulate
LU
more salt, resulting in higher corrosion rates.
Another effect of exposure and building orientation is related to the duration of surface wetness. Open
exposures dry more readily because they are exposed to sunlight, and rapid drying slows the corrosion
rate. Partially sheltered exposures stay damp longer and therefore may corrode faster.
6.5 Weather and Rates of Corrosion
Weather affects the rate of corrosion of metal in both coastal and inland locations. Most chemical
reactions, including corrosion, are affected by temperature, humidity, wind speed, and other factors.
Higher temperatures and higher humidity increase corrosion rates. Like any weather-driven condition,
corrosion rates can vary considerably from year to year.
Short-term measurements of corrosion rates at specific locations can be misleading unless compared to
long-term averages for nearby locations because average weather conditions for factors such as rainfall
seldom occur. In any given year, measured rainfall can be much higher or lower than the average rainfall.
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As a result, the corrosion rate for a given area in an individual year may be significantly higher or lower
than the long-term average rate. Because corrosion rates vary, inspections and maintenance should be
done at least annually, and preferably more often, to identify connectors and fasteners that need to be
replaced. See Section 9.2 for more information on maintenance and replacement.
6.6 IdentifyingiCorrosion Rates
Corrosion tests can help define the coastal areas where corrosion is most severe, and extra precautions
should be taken to minimize corrosion of metal connectors and fasteners. Unfortunately, corrosion data
are not available for most coastal communities, and building professionals must rely on local experience
to estimate the areas where corrosion-resistant materials and methods are needed.
Areas of increased corrosion concern can be identified by observing the state of corrosion of metal
00
connectors and fasteners in older buildings located at various distances from the shoreline. The S
observations can be documented and used to delineate areas with higher corrosion rates. Alternatively, 2
communities or builders can conduct field tests using a test kit or laboratory to determine areas where
increased corrosion protection should be used.
7 Exposure Classes for Connectors W
00
and Fasteners e0
1
Corrosion exposure types for metal �.
Interior
connectors and fasteners in most Vented enclosed living space
buildings can be grouped into five classes, exposure exposures
(includes all
which are discussed in this section. conditioned
The five classes and their locations in a Unvented spaces) 00
building are shown in Figure 6. enclosedexposure
Exposure classes should be considered (wall cavity)
when determining which connectors / U_
and fasteners are appropriate for a '
given application. The use of corrosion- %l
resistant fasteners and connectors, such
as those that are made of stainless steel Q
or incorporate thicker zinc galvanizing
(G185 or thicker), will reduce corrosion
rates or extend the period that the
Open Partially
zinc coating protects the base metal. exposed sheltered
Using corrosion-resistant fasteners and exterior exterior
exposure exposure
connectors will maintain the designed
load path longer than nominally
galvanized connectors and fasteners.
In areas where corrosion is the most ..... ,
Figure 6: Corrosion exposure classes and their locations
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Table 6. Guidance for Specific Components(concluded)
problematic, the most corrosion-resistant metal connectors and fasteners, such as Type 304 or Type 316
stainless steel, should be used.
SELECTING FASTENERS AND CONNECTORS
Before selecting fasteners and connectors, consult the locally applicable code and relevant design
standards for requirements to determine the minimum level of corrosion protection necessary.
7.1 PartiallyIExterior Exposure
Examples of partially sheltered exterior exposures are open,under-house storage;parking areas below a piling-,
column-, or post-supported buildings; and areas under roof overhangs, decks, screened-in porches, and
M
walkways. 00
In partially sheltered areas, corrosion can significantly weaken nominally galvanized light gauge metal
connectors in 5 to 10 years or sooner. When not concealed by exterior finishes, these areas can often be
co
inspected to evaluate the condition of the connectors and determine when maintenance or replacement @
0
is necessary.
0
7.2 Open Exposed Exterior
Open exposed exterior exposures are areas such as exterior LU
walls where metal connectors and fasteners are exposed G L I CTI 00
AND MAINTENANCE Q
to the elements. LO
Owners may not be aware that
If metal connectors and fasteners are exposed to rainwater
maintenance is necessary for connectors
and usually dry fully between wettings from ocean spray, and fasteners and may not be able to
as can occur in open exposed exterior exposures, the
inspect some areas where corrosion
corrosion rates will likely be lower than in partially can occur. Owners should be advised to z
sheltered exterior exposures. However, if fasteners and regularly inspect connections and that MI
00
connectors in open exposed exterior exposures do not replacement of metal connectors and ono
benefit from rainwater washes or remain wet for extended fasteners may be necessary to maintain i
periods, the corrosion rates in these exposures can match the structural integrity of their buildings. In
the rates in partially sheltered exterior exposures. areas where inspections or replacements U_
are difficult and corrosion is possible,
Connectors in open exposed exterior exposures can designers and builders should use
usually be inspected to evaluate their condition, and if materials with higher degrees of corrosion
access is sufficient to remove the fasteners, connectors can resistance, such as stainless steel. 2
often be replaced if found to be weakened by corrosion.
7.3 Vented Enclosed
Examples of vented enclosed exposures are attics, which must be vented to release excess heat and moisture,
and rafter and floor cavities if vents are installed.
Corrosion of metal connectors and fasteners in vented enclosed exposures depends on the location of the
metal connectors in the enclosed space. Corrosion rates near vents,where outside airflow is concentrated,
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are often similar to the rates in partially sheltered exterior exposures (see Section 7.1). Corrosion rates for
metal connectors that are not near vents or that are covered by insulation are expected to be much lower.
Some vented enclosed areas can be hard to access, complicating inspections to evaluate the condition of
the metal connectors and replace them when needed. In these locations, it is worth considering a more
corrosion-resistant metal connector since its condition will rarely be evaluated.
7.4 Unvented EnclosedExposures
Examples of unvented enclosed exposures are enclosed areas such as wall cavities, enclosures surrounded by
breakaway walls under elevated buildings, and floor framing cavities created when finishes are installed
on the underside of floor joists.
CL
Because of the limited airflow and incoming salt spray, corrosion rates for connectors in these exposures 00
are expected to be lower than the rates in partially sheltered exterior exposures, open exposed exterior S
exposures, or vented enclosed exposures. However, since many connectors and fasteners installed in
unvented enclosed exposures are concealed by finishes and would require removing building materials
to gain access to the fasteners, inspection to evaluate their condition is generally impractical. Therefore,
installing corrosion-resistant (or more corrosion-resistant) fasteners and metal connectors in these areas
ca
should be considered a responsible construction practice.
7.5 InteriorLivingW
Interior living space exposures are the areas within a building that are usually heated or air conditioned. °CD
D
LO
These spaces are sealed from most salt spray, and the humidity control provided in most conditioned
spaces generally reduces humidity levels below those that contribute to accelerated corrosion rates.
In coastal areas, using more corrosion-resistant fasteners such as mechanically galvanized fasteners will
better protect connections in the interior portions of exterior walls and wall connections to attic spaces z
as long as they do not receive salt spray. These areas typically have a relatively low chance of corrosion M00
and are free of preservative-treated lumber. Fasteners for interior walls can be uncoated or electroplated CO
galvanized fasteners.Materials and Coatings <
LL
8 Improving Corrosion-Resistant
0
The durability of metal connectors can be improved by using more corrosion-resistant materials such
as Type 304 or Type 316 stainless steel or by treating metal connectors after fabrication with hot-dip or
mechanical galvanizing. Improving corrosion resistance is discussed in this section.
Materials with improved corrosion resistance may cost more initially, but reduced maintenance over the
life of a building can partially or completely offset the cost.
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Another important consideration in selecting connectors and fasteners is accessibility of the connections.
Fasteners and metal connectors located in areas that cannot be readily inspected or where the fasteners
and metal connectors cannot be easily replaced should be made of materials with higher corrosion
resistance. Since corrosion not only reduces the strength of a connection, but more importantly, can
result in a load path failure, it is important to use durable connectors in building areas that are difficult
to access.
Metals may be selected because of their strength,
temperature resistance, durability, availability, cost, and More anodic
CORRODED
other reasons. As mentioned in Section 5.1.2, dissimilar
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIII Magnesium
metals can undergo a process called galvanic corrosion if Zinc
they come into contact with an electrolyte such as saltwater. aCL
When in contact with an electrolyte, charged particles flow Aluminum MM
between the dissimilar metals, which causes one of them Steel
Lead 00
to corrode and the other to be protected. Which metal
Tin
corrodes and which one is protected depends on the relative ®p
Nickel
affinity to attract or repel electrical changes. The reactivity,
Brass
the rate of corrosion that occurs, which metal will corrode,
and which one will be protected can be evaluated using a
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIII Bronze ca
Copper
galvanic corrosion chart such as the one shown In Figure 7. � Stainless Steel �
The chart shown in Figure 7 is simplified, but it shows Graphite LU
individual metals' relative affinity for attracting or repelling More cathodic
PROTECTED00
electrical charges. Metals closer to the top of the chart tend LO
to function as anodes and undergo galvanic corrosion. Figure 7: Galvanic chart of common metals
Metals closer to the bottom tend to function as cathodes
and are protected. Metals function as anodes or cathodes
i
depending on the metal they are paired with. For example, nickel will function as a cathode and be
protected when in contact with zinc or aluminum but will function as an anode and corrode when in z
contact with copper. Metals not affected by galvanic corrosion can still corrode through exposure to 0i
compounds like salt.
i
In addition to depicting which metals will function as anodes and cathodes, a galvanic chart can also
depict the relative rate of corrosion that two metals may experience. Metals that are relatively close to LL
each other on the chart will have low rates of corrosion, while those that are more widely separated will
corrode more quickly. For example, when exposed to copper, bronze, which is relatively close to copper
E
on the galvanic chart, will have a lower corrosion rate than steel, which is more widely separated from ca
copper on the chart.
The strength of the electrolyte also comes into play. For any two dissimilar metals, the anodic metal
will corrode more rapidly in an electrolyte that easily conducts electrical charges compared to a weaker
electrolyte that does not easily conduct charges. Because of this, dissimilar metals in dryer environments,
which tend to retard the flow of electrical charges, have lower corrosion rates than the same metals in
areas with high moisture levels.
As shown by its location near the "Protected" end of the chart, stainless steel is more resistant to galvanic
corrosion than most metals and is therefore the preferred metal in harsh environments and in areas
where connector replacement will be difficult.
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The galvanizing zinc protects steel in two ways: it acts as a physical barrier, and it slows the corrosion
process because the zinc layer corrodes first, even protecting adjacent scratches in the coating. It should
be noted that if a galvanized fastener is used in conjunction with steel plates, the galvanizing on the
fastener will corrode much faster than when used in conjunction with galvanized plates.
®1 Thicker Galvanizing
The galvanizing process does not eliminate the need for maintenance, but proper material selection can
prolong the lifespan of the material and increase the potential for the fastener or metal connector to
maintain its design strength. Increasing the thickness of the galvanized coating extends the length of
time before the zinc corrodes to the point where the steel base metal begins to corrode.
The two methods of producing thicker galvanized coating on connectors are:
00
• Fabricating connectors from steel sheet with thicker initial galvanized coating S
• Galvanizing connectors after fabrication
Galvanized sheet steel is available in a variety of coating thicknesses. Several manufacturers now market
common connectors in various designs fabricated with G185 to G200 grades of galvanized protection,
which, compared to standard G60 or G90 grades, have zinc coatings that are two to three times thicker.
Since the corrosion resistance of zinc is proportional to the thickness of the zinc, G185 to G200 connectors Q
should last approximately two to three times longer than G60 or G90 connectors. LU
Thicker galvanized coatings can also be attained by using the hot-dip process after connector fabrication. 00
Several variables can affect the thickness of hot-dip galvanizing,but the result is typically a coating of zinc LO
similar to the coating on a G185 connector.A few types of connectors with thicker galvanized coatings are
regularly available. Other connector designs are available by special order.
Figure 8 illustrates that increasing the thickness of galvanizing results in a longer service life. The extent
to which service life is increased depends on the location and the amount of salt in the air, as well as z
pollutants such as sulfur dioxide. LEI
00
Rural LU
4i
Suburban
000
Temperate Marine
m .'�N
u" Tropical Marine
w,umww00- „wwummo, Moderate Industrial
wm w ww www w
N '000 mu ww w"m wm
mw w"' wmunrw^uNtlwmwuumn �uuuumu' a „ � °�� Heavy Industrial
aoou
wuwwn' tl mww"""'w um' �wwwwNA"'ww mwiwiwwumuumw'°'^ ""
wwuiwumwiwuww""
uuum
G60 G90 G140 G185 G235 G300
Coating Weight Designation (ASTM A653)
Figure 8:Approximate service life improvement from increasing galvanization thickness
SOURCE:ADAPTED FROM ZHANG(2002)
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Applying an additional outer coating in the factory or painting light gauge metal connectors fabricated
from galvanized steel can enhance corrosion protection (see Section 8.3), and manufacturers can provide
data on appropriate applications and compatible fasteners. However, paint should be used with caution
because if it is scratched, it does not provide any corrosion resistance at that location.
8.2 Stainlessi
Stainless steel is created when other metals are added to steel to make an alloy. The composition of the
alloy determines its corrosion resistance, temperature resistance, and hardness and denotes the stainless
steel type. Not all types of stainless steel have the same corrosion resistance, and some types are preferred
over others in saltwater applications. Several connector manufacturers produce the most commonly used
connectors in a stainless steel option. Stainless steel is resistant to corrosion in salt air, and it usually lasts 0
longer than most other materials, even in the most corrosive oceanfront situations. 00
To eliminate the potential for galvanic corrosion, stainless steel connectors must be attached with stainless 2
steel nails when separate fasteners are needed; otherwise, corrosion will be accelerated on the less
corrosion-resistant metal and can dramatically reduce its lifespan (see Figure 7). In coastal applications,
stainless steel should be Type 304 or Type 316. Type 316 is more resistant to corrosion and should be used r_
for stainless steel metal connectors. Some fasteners are fabricated from Type 410 stainless steel,which has
more corrosion resistance than galvanized bare steel but less than Type 316 stainless steel.
Stainless steel is tougher than normal carbon steel, which means that stainless steel connectors are more LU
LL
difficult to fabricate. Also, stainless steel tends to be more expensive than carbon steel and galvanized —
00
steel.When considering upgrading from galvanized fasteners and connectors to stainless steel, designers, CD
CD
contractors, and building owners in coastal areas should compare the cost of stainless steel connectors to
G185 galvanized connectors, not to G60 and G90 galvanized connectors, which are not recommended
in coastal areas. Furthermore, the reduced maintenance/replacement/labor life-cycle costs when using CD
stainless steel should be considered when specifying connectors. See Section 9.2.2 for further details. _'
8.3 AppliedI I '
Coatings and paint applied to galvanized steel connectors can improve corrosion resistance, but many
coatings and paints commonly used for buildings do not adhere well to galvanized surfaces. The Truss
LU
Plate Institute (TPI) has evaluated the use of truss plates in corrosive environments. If specified by the �
registered design professional or building designer, ANSI/TPI 1-2014 design specifications, which are
referenced in the I-Codes, recommend that one of two industrial paint systems be applied by brush to
embedded plates after delivery of the completed truss to the job site or after truss installation (ANSI/TPI,
2014). Alternatively, using truss plates with a thicker hot-dip galvanized coating is also recommended.
The three industrial coating options for increasing corrosion resistance are:
• Epoxy-polyamide primer (SSPC-Paint 22)
• Coal tar epoxy-polyamide black or dark red paint (SSPC-Paint 16)
• Post-plate manufacture hot-dip galvanizing (zinc-based) per ASTM A153/AI53M (ASTM, 2016)
The degree of improvement in corrosion resistance that the recommended applied coatings provide is
difficult to estimate. Unlike differences in galvanized coating thickness,differences in paint system coating
thickness do not proportionally change the corrosion resistance of the connector. Coating lifetimes are
20 NFIP TECHNICAL BULLETIN
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significantly affected by salt spray,but exposure conditions can affect coatings and galvanizing differently.
Surface preparation and care in application are critical for improving corrosion resistance with coatings.
The added cost of these coatings varies with local labor costs.
In general, other types of coatings and paints should not be assumed to significantly improve the
corrosion resistance of nominally galvanized connectors and truss plates. For other types of connectors,
the alternatives described previously are recommended over any other type of painting. However, for
maintenance, zinc-based coatings may offer some benefits over standard coatings because zinc-based
coatings can increase protection somewhat in areas where the coating is damaged. Stainless steel metal
connectors should not be painted because the coating can prevent the protective oxide film that forms on
the surface of stainless steel from developing. This oxide film is how the stainless steel resists corrosion.
8.4 Other Corrosion-Resistant
Manufacturers supply some fasteners with coatings other
than galvanization and should be evaluated to ensure ADDITIONAL INFORMATION C �
their corrosion resistance. ICC Evaluation Service (ICC- CONNECTORS
ES) produces acceptance criteria that manufacturers use
Additional information on properly
to demonstrate that product performance is consistent making connections between the
with I Code requirements. ICC-ES published AC257, foundation and the building can be found
Acceptance Criteria for Corrosion-Resistant Fasteners and 2
in FEMA's Hurricane Sandy Recovery w
Evaluation of Corrosion Effects of Wood Treatment Chemicals Advisory RA1, Improving Connections in
(ICC ES, 2015), which provides criteria for alternative Elevated Coastal Residential Buildings 00
fasteners. The criteria outline requirements for testing (2013). The recovery advisory also L�
fasteners in preservative-treated lumber in various types discusses corrosion protection and lists
of accelerated corrosion environments. There are also resources for strengthening connections
evaluation reports regarding this acceptance criterion in wood-framed buildings.
that provide information so that fasteners that are
not galvanized or stainless steel can be considered for LEI
applicability in coastal environments. Without an evaluation report, manufacturers can often provide 00
some information to allow comparisons with other more common methods of fabricating corrosion-
resistant fasteners.
9 Guidance for Connector and Fastener
LU
Corrosion Control <
In corrosive environments, most construction materials deteriorate with time and eventually need
to be repaired or replaced. In the United States, the service life of a wood-frame building could be
approximately 70 years or more. With continued maintenance and periodic upgrades, buildings can
remain serviceable well beyond that time. However, lack of maintenance and repairs can cause buildings
to deteriorate much sooner than the average service life. Buildings located in coastal environments where
NFIP TECHNICAL BULLETIN 8 JUNE 2019 91
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steel components can corrode at a high rate are particularly susceptible to deterioration if not maintained
regularly. Continued use of a building over its service life requires that:
• The original materials are durable enough to last the expected lifetime
• Periodic maintenance is conducted to extend the life of original materials
• Materials that have deteriorated are replaced
®1 Reducing Corrosion
Standard connectors are intended for inland uses, and under normal conditions, they last as long or
longer than other materials in a building.Although components of some buildings in coastal communities a
0.
may have only slightly increased corrosion rates, buildings close to the ocean are likely to have drastically D
00
higher corrosion rates. In nearshore areas, the use of more corrosion-resistant materials and coatings is
recommended in partially sheltered exterior exposures, open exposed exterior exposures, vented enclosed exposures, a�
and unvented enclosed exposures (see Figure 6). Use of nominally galvanized metal connectors should be
limited to interior areas that can be protected from corrosion (interior living space exposures).
ca
Additional considerations in reducing corrosion rates are as follows:
ca
• Consider changing the exposure class where connectors are used. For some uses, corrosion rates can
be reduced by altering the exposure of the connectors. For example:
w
— Connectors typically found on building exteriors should be fully covered if possible or otherwise .�
protected from salt spray and moisture.Applying exterior siding to fully cover the connections is 00
one way to change the exposure from open exposed exterior exposure to an unvented enclosed exposure L�
condition.
— An easy way to protect joist hangers and truss plates in the floors of piling-supported buildings is
to sheath the underside of the floor joists to reduce the exposure to salt air. Adding such sheathing
transforms one of the worst exposures,partially sheltered exterior exposure, into the less corrosive _
unvented enclosed exposure condition. However,when corrosion occurs, it can go undetected, so screws LEI
or some other removable fastening mechanism should be used to allow periodic inspection. o00o
• Consider using alternate materials or connection methods. For some connections, such as floor joist-
to-floor beam connections, corrosion may be minimized by not using light gauge metal connectors, LU
especially in partially sheltered exterior exposures and open exposed exterior exposures. Construction practices
that were commonplace before the advent of light gauge metal connectors can be used to connect
wood framing.With many of those practices, metal fasteners (nails,wood screws, lag screws, and
bolts) are used with wood framing, and the metal fasteners are nearly fully concealed and protected
from the elements by the wood components. In many connections, only the head of the fasteners
remain exposed to salt spray.When used with preservative-treated lumber, stainless steel nails and
other corrosion-resistant fasteners should be used. See Section 9.2 for more guidance on maintenance
and replacement. See the applicable building code for information on when these alternate methods
are permitted and the size and number of fasteners that are required.
Figure 9 and Figure 10 show common methods of connecting wood framing members with only nails,
screws, lag screws, and bolts. In both methods, the shafts of the fasteners are not exposed to salt spray.
22 NFIP TECHNICAL BULLETIN
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The drawback of these methods is that their capacity to resist loads is not readily known since their
strength depends greatly on fastener sizes and even more on the species of wood used. The design of
wood framing connections is complex, and prescriptive methods are somewhat limited. The IRC and
the Wood Frame Construction Manual (AWC, 2015) both contain nailing schedules, but neither contain
prescriptive methods for connections such as those shown in Figure 10 and Figure 11. In contrast, the
capacities of light gauge metal connectors are published by the manufacturers and verified by third-party
testing. See the textbox below for more information.
Floor joists lapped
Double-band joist', over beam
Floor joist(notched) CL
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, o
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Floor joist
Ledger Wood uplift block cut from not LU
board Interior less than graded 2x4 nominal
beam dimension lumber 00
Nails through ledger board
into double-band joist Full-depth solid blocking 'oi
Floor
at �� g����������������
Figure 9:Traditional wooden ledger boards used in place
sheV.-
of joist hangers in high corrosion areas
i Lapped joists
wind anchors % Using staggered 0i
® ® nailing,face-nail CO
® uplift block to
Beam beam, and joist
® ® to uplift block
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Section A
Floor Figure 10: Detail of an elevated floor-to-beam connection
f joist
Floor using wood uplift blocking and full-depth solid blocking
Nails through beams
beams into
wind anchors
Bolts through beams and pile
Square
wood pile
Figure 11:Wooden wind anchors used to connect floor joists
to floor beams
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STRENGTHS OF NAILED, SCREWED, LAGGED,AND BOLTEDCONNECTIONS
The strength of connections made with dowel-type fasteners (nails, screws, lag screws, bolts, split ring
connectors, shear plate connections, and timber rivets) is specified by ANSI/AWC NDS-15, National Design
Specification for Wood Construction (2014a).
Allowable loads are determined by multiplying reference design values by all applicable adjustment factors.
The reference design values are tabulated in NDS-15, Chapter 12; adjustment factors are contained in
Chapters 11 and 12. Most adjustment factors are less than 1.0 (they lower the reference design values);
several adjustment factors that account for load duration are greater than 1.0.
Reference design withdrawal values (W)for lag screws, wood screws, nails, and ring shank nails are listed
in NDS-15, Tables 12.2A through 12.2D. Adjusted withdrawal values (W') are determined by applying all0.
adjustment factors to those reference withdrawal values. Reference design withdrawal values and adjusted
00
withdrawal values are measured per inch of fastener penetration or the depth of thread penetration for
threaded fasteners.
Reference design lateral values(Z)for bolts, lag screws, wood screws, nails, and ring shank nails are
tabulated in NDS, Tables 12A through 121 Like withdrawal values, adjusted lateral design values (Z') are 2
obtained by multiplying reference values by all adjustment factors.
The design values in the NDS are only for fasteners meeting the generic specification for that particular
type of fastener. Fastener manufacturers have recently begun developing improved proprietary fasteners
with higher design values. These design values can typically be found in the fastener's evaluation report. LU
00
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9.2 MaintenanceIConsiderations
Inspection of fasteners and metal connectors is important and should be a regular maintenance activity �-
undertaken by owners of buildings located in nearshore coastal environments. Since many homeowners may _�
not be aware of the effects of corrosion on the fasteners in their homes, communities in coastal areas should consider z
communicating to their citizens the importance of routine inspection and maintenance of connectors and fasteners. LEI
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In some applications, connectors may be located where they are accessible and easily maintained. In areas
where corrosion is less aggressive, such as locations farther from the coast, applying a coat of exterior
house paint to exposed connectors may be enough to extend the life of the connectors. In areas with LU
LL
more aggressive corrosion, even annual painting is unlikely to prolong the life of connectors. In these
areas, accessible connectors should be inspected for corrosion and replaced when necessary. Galvanized E
light gauge metal connectors should be replaced as soon as corrosion extends into the base metal (see
ca
Figure 12).The presence of more than thin rusty edges indicates that the zinc coating has been consumed
and the sacrificial effects have been lost. Corrosion of the thin, steel sheet will occur quickly and rapidly
affect the structural integrity of the connector.
24 NFIP TECHNICAL BULLETIN
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(rust) is extending into the 00
metal, resulting in the loss of r_
effective anodic protection and rapid
deterioration of the light gauge metal
connectors, necessitating connector
replacement.
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Figure 12:Zinc galvanizing on connectors that has corroded LU
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®2.1 Replacing Corrodede t r
Replacement is the only option in existing buildings where connectors have already been damaged by �.
corrosion. It is recommended that replacement connectors have different sizes or shapes or be fastened
in different locations so that connections are to undisturbed wood. Since the availability of locations
to attach replacement connectors into undisturbed wood may be limited, it is imperative that the most M�
corrosion-resistant connectors and fasteners possible be used to minimize replacements over the life of 00
the structure. Inspections may also indicate a need to install connectors where they were not previously
installed. For example, adding roof uplift connectors (hurricane clips) can significantly improve wind
LU
resistance and is generally worthwhile, even if some dismantling is needed to gain access. Wind retrofits LL
are described for various levels of wind performance improvement in FEMA P-804, Wind Retrofit Guide for
Residential Buildings (2010c). as
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®2.2 Reducing Connectionai to a ce for New and Existingit in s
When evaluating the option of whether to initially install more corrosion-resistant metal connectors or
replace them more frequently, the cost over the life of the building should be considered. Enhanced
corrosion-resistant metal connectors, available for a moderately higher price, can have significantly longer
lifetimes than nominally galvanized connectors. The cost of labor for initial installation is often the same
for either option. The material and labor cost for even one replacement is typically many times more than
the added cost of initially installing more corrosion-resistant materials. Using more corrosion-resistant
materials during construction can avoid or reduce the cost of future repairs.
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In areas where conditions foster aggressive corrosion and nominally galvanized connectors may have to
be replaced as often as every 5 years, using more expensive materials such as stainless steel connectors
and fasteners will likely prove less costly over the long run. Repeated replacement of metal connectors can
be difficult since previously used fastener holes should not be reused. Different styles of metal connectors
may provide different and faster locations to facilitate replacement, but eventually damage from fastener
holes may result in the need for more extensive repairs such as replacing structural members to maintain a
continuous load path. Replacing structural members would be more expensive than upgrading to a more
corrosion-resistant metal connector that would reduce the number of necessary connector replacements
over the life of the building.
Given the difficulty of inspecting many connections after construction and the impossibility of inspecting
others without invasive actions, using nominally galvanized fasteners and metal connectors in corrosive 'a0.
areas is fraught with potential problems and higher maintenance costs. There is a low likelihood that M
00
effective regular inspections to identify deterioration before the structural integrity is compromised r_
would or could be performed. Even when problems with more vulnerable connectors can be identified, 2
75
replacing damaged connections in existing buildings is usually costly and difficult. Furthermore, many
connectors are hidden structural components that will go unseen and are difficult or impossible to
maintain or replace. In such cases, replacement is rarely an option, and more corrosion-resistant materials
should be selected during initial construction.
LU
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10 Summary of Best Practices Q
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for Corrosion Resistance
1
For many connector applications in corrosion-prone buildings, using materials with enhanced corrosion
resistance is the best solution for new construction, and is also recommended for replacement connectors L00
during maintenance or repair/renovation of existing construction. The choice of alternative connector
material or coating specification should be guided by the following criteria: �I
• Location of the building relative to the observed corrosion hazards (primarily distance from the LU
coast), as noted in Section 6 U_
• Where the connectors will be used, as noted in Section 7 E
• Importance of the connection to the structure's load path, as noted in Section 4
• Life-cycle cost-effectiveness of the connector for the structure's service life, as noted in Section 9
• Long-term viability of the structure based on its potential service life and the need to maintain a
proper load path throughout the life of the structure
Recommended materials for typical residential buildings are listed in Table 3.
In Table 3, building locations are identified as oceanfront buildings, intermediate rows of buildings in
corrosion-prone areas, and buildings near the coast but far enough away from the ocean that excessive
corrosion is not anticipated or has not been observed. Metal connectors with minimal galvanizing on
oceanfront buildings are expected to corrode at high rates. In most communities, as buildings are
26 NFIP TECHNICAL BULLETIN
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constructed farther from the oceanfront, the rate at which corrosion occurs should decrease significantly
at distances of 300 to 3,000 feet landward of the ocean. FEMAs Mitigation Assessment Team deployed
to Puerto Rico following Hurricanes Irma and Maria and identified areas farther inland than 3,000 feet
landward of the ocean where significant corrosion was noted on exposed structural connection that would
be more consistent with the corrosion experienced by buildings closer to the shoreline (FEMA, 2018b).
This finding suggests that in some areas, building owners may want to consider using hot-dip galvanized
or stainless steel connectors farther inland than the 3,000 feet landward of the ocean guideline.
A site survey of surrounding buildings and structures may provide information on the severity of
corrosion in specific areas,which will affect the useful life of connectors and fasteners.Another key factor
for material selection is the exposure class of the connectors and fasteners; exposure classes are listed
in Table 3 in order of decreasing severity of corrosion at particular locations. Since access to inspect a
or replace connectors and fasteners is a key consideration in whether to use more corrosion-resistant D
00
materials, an assessment of the severity of corrosion in the area and exposure class may provide additional
insight into whether to use upgraded fasteners and connectors.
Table 3 also includes notes on truss plate treatments based on TPI recommendations for corrosive
environments. Some of the recommendations in Table 3 are based on limited research.When the severity ca
of the exposure is unknown, selecting more corrosion-resistant materials is prudent. In most cases, a Type
304 or Type 316 stainless steel connection or fastener will provide superior corrosion resistance, as shown
in the galvanic corrosion chart in Figure 7.
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Table 3: Recommendations on Corrosion-Resistant Materials and MethodsCD
.�
MMIEMEMEM
LO
I
Partially Sheltered Easy • Avoid light gauge metal • Use connectors with • Use connectors
Exterior Enclosures connectors thicker galvanized with code-required
• Use stainless steel coating galvanizing
connectors and • Best practice: • Best practice: Use ®I
fasteners Use stainless steel connectors with thicker 00
co
• Use connectors with connectors and galvanizing than
thicker galvanizing and fasteners required by code or use
replace when necessary stainless steel
LU
Open Exposed Easy • Avoid light gauge metal Use connectors with Use connectors
Exterior Enclosures connectors a thicker galvanized with code-required
• Use stainless steel coating galvanizing
connectors and Best practice: Best practice: Use
fasteners Use stainless steel connectors with thicker
• Use connectors with connectors and galvanizing than
thicker galvanizing fasteners required by code or use
stainless steel
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Table 3: Recommendations on Corrosion-Resistant Materials and Methods(concluded)
MMIEMEMEM
Vented Enclosed Difficult • Use connectors with • Use connectors with • Use connectors
Exposures thicker galvanizing a thicker galvanized with code-required
• Best practice: coating galvanizing
Use stainless steel • Use TPI-specified • Best practice: Use
connectors and coatings on truss plates connectors with thicker
fasteners near vents galvanizing than
• Use TPI-specified • Best practice: Use required by code or use
coatings or paints on thicker galvanizing stainless steel
truss plates for all connectors; CL
• Best practice for use stainless steel
00
truss plates: Use TPI- near vents or where
specified coatings over salt accumulation is
thicker galvanizing, or anticipated
use stainless steel
2
Unvented Difficult • Use connectors with • Use galvanized • Use connectors
Enclosed thicker galvanizing connectors with code-required
Exposures • Use TPI-specified • Best practice: Use galvanizing
coatings or paints on connectors with thicker • Best practice: Use
truss plates galvanizing than connectors with thicker
• Best practice for truss required by code or use galvanizing than
plates: Use thicker stainless steel required by code or use 00
galvanizing or use stainless steel LO
stainless steel.
Interior Living Difficult • Use galvanized • Use galvanized • Use galvanized
Space Enclosures connectors connectors connectors
• Best practice: Use • Best practice: Use • Best practice: Use
thicker galvanizing than connectors with thicker connectors with thicker
required by code or use galvanizing than galvanizing than 00
stainless steel required by code or use required by code or use
stainless steel stainless steel
The recommendations in this table are based on available research and are subject to change in future Technical Bulletins.Stainless steel connec-
tors should also be considered a best practice in many of the areas listed in the table.However,due to practical and cost reasons,this guidance
does not prescribe its use,although the galvanic corrosion chart(Figure 7)clearly shows that stainless steel(especially Types 304 and 316)is a
superior performer for corrosion resistance compared to many other metals. 0
(1) See Section 7 for information on exposure classes.
(2) Ability to inspect/replace fasteners and connectors.
(3) 300 feet or less from the shoreline. Distances may vary depending on local climate.The width of corrosion-prone areas relative to the ocean
should be determined from field observations,existing corrosion studies,and consultation with local building departments.
(4) Greater than 3,000 feet from the shoreline.Distances may vary depending on local climate and can extend much farther inland as identified by
FEMA's Mitigation Assessment Team in Puerto Rico(FEMA,2018b).The width of corrosion-prone areas relative to the ocean should be deter-
mined from field observations,existing corrosion studies,and consultation with local building departments.
28 NFIP TECHNICAL BULLETIN
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11 References and Resources
This section lists the references that are cited in this Technical Bulletin (Section 11.1) and additional
resources on wood-framed building connection requirements (Section 11.2). Additional resources are
listed in Technical Bulletin 0.
11®1 References
ANSI/AWC (American National Standards Institute /American Wood Council). 2014a. NDS: National
Design Specification for Wood Construction. NDS-15.Available at slab ➢arils/
M
p ub is al lolls/. 00
ANSI/AWC. 2014b. PWF:Permanent Wood Foundation Design Specification with Commentary, 2015 Edition. a�
PWF-2015.Available at iauu�::s://cc�v� .du�cc�.ai,/�:�➢�/c�a�c➢c s.sudu �cicuc➢ / .:cui ➢ic� . ia� �s/ .:���/ Wi; I"WI �➢i 7...
CollmwJllaryvlccw(hdy i� ii.pdi'.
.2
ANSI/TPI (American National Standards Institute / Truss Plate Institute). 2014. National Design Standard ca
forMetal Plate Connected Wood Truss Construction.ANSI/TPI 12014.Available at hll ps://www.0 puilsi.
org/upi sio cVaiisiupi 1..20K
ASCE/SEI (American Society of Civil Engineers / Structural Engineering Institute). 2005. .�
Flood Resistant Design and Construction.ASCE 24-05.Available at hilps://duscc.➢ibrarr�,.a�rg/dol/ Q
ASCE/SEI. 2014. Flood Resistant Design and Construction.ASCE 24-14.Available at hilps://duscc.➢lbra y,org/ �.
ASCE/SEI. 2016. Minimum Design Loads and Associated Criteria for Buildings and Other Structures.ASCE 7-16.
Available at hilps://duscc.➢ 1.0,1061/97(11 ➢07ty�� i�Nt,1�. 00
ASTM (ASTM International). 2004. Standard Specification for Coatings of Zinc Mechanically Deposited on Iron
and Steel.ASTM B695-04.Available at hit ps://www, su m.org/.
U_
ASTM. 2015a. Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated
as
(Galvannealed)by the Hot-Dip Process.ASTM A653/A653M-15.Available at hil ps://www,asu m.org/.
0
ASTM. 2015b. Standard Specification for Zinc (Hot Dip Galvanized) Coatings on Iron and Steel Products.ASTM
A123/A123M-15.Available at i ilps://www, sim, rrgy/.
ASTM. 2016. Standard Specification for Zinc Coating(Hot-Dip) on Iron and Steel Hardware.ASTM A153/
A153M-16.Available at i ilps://www, sum.org/.
AWC (American Wood Council). 2015. Wood Frame Construction Manual. Available at Mips://awc.orrg/
codes S1ailc➢ardS/plIb➢ucall oil S/.
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FEMA (Federal Emergency Management Agency).Various. NFIP Technical Bulletins. Current editions
available at techti�cfl I ilffledfls:
— User's Guide to Technical Bulletins. NFIP Technical Bulletin 0.
— Flood Damage-Resistant Materials Requirements for Buildings Located in Special Flood Hazard Areas. NFIP
Technical Bulletin 2.
FEMA. 2010a. Home Builder's Guide to Coastal Construction. FEMA P-499.Available at hil ps://www,fcum-
�,a�s�/��n:.�➢�� ➢un���.�r�,-/du����ru�/�➢a����u��n:.����/��na�:n..
FEMA. 2010b. Substantial Improvement/Substantial Damage Desk Reference. FEMA P 758.Available at III I ps://
������.�u.uuu�..�,a�s/�aruu.u➢udu ��n��dua!y/du��ur�s/�➢a�u�uu�suu.uu� /n�,,���. �
FEMA. 2010c. Wind Retrofit Guide for Residential Buildings. FEMA P-804.Available at III ps://w ww,fc1IIa, 00
�,a�s�/��n:.�➢�� ➢un���.�r�,-/du��c�ru�/�➢a����u��n:.����/�n�i���.
FEMA. 2013.Improving Connections in Elevated Coastal Residential Buildings. Hurricane Sandy Recovery
Advisory#1.Available at III I ps://wwwSC1 I I a''oN'/I1Tclu➢udu �lbr ury/asscis/docllIITcJ4u /30 966. �
FEMA. 2018a. Answers to Questions About Substantially Improved/Substantially Damaged Buildings. FEMA 213.
Available at huu l �lbr ury/asscis/u➢ocllllwJuu /169099. �
FEMA. 2018b. Hurricanes Irma and Maria in Puerto Rico—Building Performance, Observations, LU
Recommendations, and Technical Guidance. FEMA P-2020.Available at iauu
00
��wM cra CD
mc��ciudu ➢u du ��/dssuru /� c�u�uuuuu�°s �u /n./rr/Q�..i. LO
ICC (International Code Council). 2012, 2015, 2018. International Building Code.Available at iail ps://
ICC. 2012, 2015, 2018. International Residential Code.Available at hiu�:us://������. u�u� du�ur.c� �;,/.
ICC. 2018. International Existing Building Code.Available at hilps://www,lccsaf::r.o ,;,/. 00�
ICC-ES (ICC Evaluation Service). 2015. Acceptance Criteria for Corrosion-Resistant Fasteners and Evaluation of
Corrosion Effects of Wood Treatment Chemicals.AC257.Available at III ps://Icc s,o g/. LU
U-
IMCIA (International Molybdenum Association). 2009. Which Stainless Steel Should Be Specified
for Exterior Applications?Available at luu.ups-//Www.11IIVo<I.�Tufo/doWTI�o Id E
Lague, F.L. 1975. Marine Corrosion: Causes and Prevention. New York:John Wiley& Sons.
Zhang, X.G. 2002. Zinc Coating Life Predictor. International Zinc Association.Available at iaiips://
WWW.uorbc°c�"ah"col➢n/4l"/plIIiIcalI oil S/ 111c i;oalliug I_°afu. i,aulcichtic
Ou:fiobc� r ..2011 .p df.
30 NFIP TECHNICAL BULLETIN
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11.2 Resources
The following sources have additional information on wood-framed building connection requirements.
AGA (American Galvanizers Association). 2009. Hot-Dip Galvanized Fasteners:Advantages of and Design
Considerations forHot-Dip Galvanized Fasteners.Available atauu :as�// , :��du �i
AGA. 2012. Hot-Dip Galvanizing for Corrosion Protection:A Specifier's Guide.Available at
1111 iZcil'org,/.
FEMA. 2006. Hurricane Katrina in the Gulf Coast:Mitigation Assessment Team Report, Building Performance
Observations, Recommendations, and Technical Guidance. FEMA 549.Available at huu 'a
CL
� n� iidu ➢idu �/ds �ru /�i ���u� n�°s �u /��D�� .
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FEMA. 2011. Coastal Construction Manual. FEMA P-55.Available at
as
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FIP TECHNICAL BULLETIN 8 JUNE 2019
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9 MONROE COUNTY, FLORIDA
10 MONROE COUNTY BOARD OF COUNTY COMMISSIONERS
11 RESOLUTION NO. -2019
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13 A RESOLUTION OF THE MONROE COUNTY BOARD OF
14 COUNTY COMMISSIONERS ADOPTING FEMA TECHNICAL
15 BULLETIN 8 "CORROSION PROTECTION FOR METAL
16 CONNECTORS AND FASTENERS IN COASTAL AREAS" DATED
17 JUNE 2019 AS REQUIRED PURSUANT TO MONROE COUNTY 00
18 CODE SECTION 122-2(C)
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21 WHEREAS, Monroe County is currently a participating community in the National g
22 Flood Insurance Program (NFIP) and is working on internal County policies to improve upon its
23 interpretation of NFIP regulations; and
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25 WHEREAS, Monroe County desires to maintain eligibility and improve its standing in W
26 FEMA's Community Rating System (CRS); and
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28 WHEREAS, Monroe County Code Section 122-2(c), in part, requires that in interpreting i
29 other provisions of this chapter, the building official shall be guided by the current edition of 0i
30 FEMA's 44 CFR, and FEMA's interpretive letters, policy statements and technical bulletins as
31 adopted by resolution from time to time by the board of county commissioners;
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33 NOW, THEREFORE, BE IT RESOLVED BY THE BOARD OF COUNTY
34 COMMISSIONERS OF MONROE COUNTY, FLORIDA:
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36 Section 1. Pursuant to Monroe County Code Section 122-2(c), the Board hereby adopts
37 FEMA Technical Bulletin 8 "Corrosion Protection for Metal Connectors and Fasteners in
38 Coastal Areas" dated June 2019, a copy of which is attached hereto.
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40 Section 2. The Clerk of the Board is hereby directed to forward one (1) certified copy of
41 this Resolution to the Building Department.
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I PASSED AND ADOPTED by the Board of County Commissioners of Monroe County,
2 Florida, at a regular meeting held on the 181' of September, 2019.
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6 Mayor Sylvia Murphy
7 Mayor pro tem Danny L. Kolhage
8 Commissioner David Rice
9 Commissioner Heather Carruthers
10 Commissioner Michelle Coldiron
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14 BOARD OF COUNTY COMMISSIONERS
15 OF MONROE COUNTY, FLORIDA
16 M
17 BY: 00
18 Mayor Sylvia Murphy
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20 (SEAL) 00
21 ATTEST: KEVIN MADOK, CLERK 2
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24 Deputy Clerk
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FEMA Technical Bulletin Updates
Summary of Changes
NFIP Technical Bulletin 0—"User's Guide to Technical Bulletins"
Additions and updates:
• Addition of definitions including "Coastal A Zone", "Limits of Moderate Wave Action or LiMWA"
and updates to multiple definitions reflecting changes set forth in ASCE 24-14.
• Addition of descriptive and illustrative sections regarding Coastal A Zones and LiMWA CL
boundaries. 00
• References updated documents/fact sheets such as FEMA 213 "Answers to Questions About
Substantially Improved/Substantially Damaged Buildings," (August, 2018).
• Addition of Building Codes and Standard Requirements comparison showing how NFIP
regulations relate to ICC, IRC, and ASCE codes. Definitions also updated to show relevant 2
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changes to other codes. Monroe County already regulates to all codes that have higher
standards than NFIP.
• An updated 'crosswalk' of NFIP regulations, the Technical Bulletin relevant to the regulation, and
the key concepts provided therein.
• TB 0 specifically calls out detached garages in V Zones as being required to have their Lowest
Horizontal Structural Member (LHSM) elevated to or above BFE. As a note, NFIP still references
Base Flood Elevation (BFE)for requirements as 'Design Flood Elevation' requirements will vary gj
by jurisdiction. CO I
NFIP Technical Bulletin 4—"Elevator Installation"
Additions and updates: CL
• Addition of clear definition noting space of elevator equipment pit when located below grade
does not constitute a basement.
• Detailed breakdown of different styles of elevators and the requirements of equipment
locations. 2
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• Low Rise v. High Rise discussion. "For the purposes of this Technical Bulletin, "low-rise" refers to
the IRC (one-and two-family homes and townhomes not more than three stories above grade
plane) and other structures with a mean roof height of less than 75 feet. "High-rise" refers to
structures with a mean roof height of 75 feet or more."
NFIP Technical Bulletin 8—"Corrosion Protection for Metal Connectors and Fasteners in Coastal
Areas"
Additions and updates:
• Mostly guidance updates for what situations to use different corrosion-resistant fasteners and
connectors.
• Much of this is information that has been updated to reflect changes in ICC/IRC/ASCE 24
requirements. Florida Building Code meets or exceeds the guidance provided herein.
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Please note that NFIP still treats Coastal A Zones as A Zones;whereas Florida Building Code,in
conjunction with ASCE 24-14, requires municipalities to regulate these areas to V Zone standards.
There are multiple references to this throughout the updates.
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