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City and County of San Francisco London N. Breed, Mayor
Department of Building Inspection Patrick O’Riordan, C.B.O., Director
INFORMATION SHEET
No. FS-01
DATE : July 24, 2024
CATEGORY : Fire Safety
SUBJECT : Combustible Roof Decks – Allowable Materials and Area
PURPOSE : The purpose of this information sheet is to clarify standards for allowable building
materials used in the construction of roof decks that conform to the minimum
standards for resistance to intrusion and spread of flames.
REFERENCES : San Francisco Building Code (SFBC), Current Edition
Sections 104A.2.8 and 1511.10
California Building Code (CBC), Current Edition
Sections 703A.5.1, 703A.5.2, 703A.7, 709A.3, 2303.1.9, 2303.2
California Referenced Standards Code (CRSC), Current Edition
Section 12-7A-4 Decking SFM Standard 12-7A-4
Section 12-7A-4A Decking Alternate Method A SFM Standard 12-7A-4A
American Society for Testing and Materials (ASTM), E-84 Test for Surface Burning
Characteristics of Building Materials
California Department of Forestry and Fire Protection, Office of the State
Fire Marshal (OSFM) - Wildland Urban Interface (WUI) Products Handbook
BACKGROUND :
SFBC 1511.10 provides conditions under which occupiable roof decks are allowed to be constructed of wood.
SFBC 1511.10 #4 requires that the wood decking be constructed of fire-retardant treated wood material
approved for exterior use, or 2-inch nominal, All Heart redwood. SFBC 104A.2.8 allows the Building Official
to approve alternate materials when the material is at least the equivalent of that prescribed in the code. This
information sheet clarifies the standards for allowable building materials that conform to the minimum
standards for resistance to intrusion and spread of flames used in the construction of roof decks.
DISCUSSION :
All Heart redwood has been shown to conform to the ASTM E-84 Class B flame spread index and exhibit a
net peak heat release rate in conformance with Decking SFM Standard 12-7A-4 and Decking Alternative
Method A SFM Standard 12-7A-4A. As these are equivalent to the minimum standards stated in the CBC
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Technical Services Division
49 South Van Ness Avenue, Suite 500 – San Francisco, CA 94103
(628) 652-3720 – sfdbi.org
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INFORMATION SHEET FS-01
709A.3, #4 for decking used in a wildland urban interface location, materials complying with this section and
these standards may be considered equivalent and thus be allowed for use in roof deck construction.
Therefore, in order for the decking material to be considered equivalent to the requirements of SFBC
1511.10, the material must conform to the ASTM E-84 Class B flame spread index and must conform to the
requirements of SFM Standard 12-7A-4 (Part A) or SFM 12-7A-4A. It must also pass an accelerated
weathering test and be identified as exterior type in accordance with both ASTM D 2898 and ASTM D 3201.
Decking material that conforms with SFM 12-7A-4 and SFM12-7-4A, as well as ASTM D 2898 and ASTM D
3201 are listed in the current version of “California Department of Forestry and Fire Protection, Office of the
State Fire Marshal - Wildland Urban Interface Products Handbook (WUI Products Handbook)”, published by
Cal-Fire, Fire Engineering Division, Building Materials Listing Program.
Only those materials listed in the WUI Product Handbook in the Decking section and conform to the ASTM
E-84 Class B or Class A flame spread index are deemed equivalent materials that may be used for the
construction of wood roof decks. Additionally, materials not listed in the WUI Products Handbook that have
appropriate documentation showing that they conform to the above standards may also be considered
equivalent on a case-by-case basis. The WUI Products Handbook is available at the Office of the State Fire
Marshal (OSFM) website:
https://osfm.fire.ca.gov/what-we-do/fire-engineering-and-investigations/building-materials-listing
Materials must be installed in conformance with the structural provisions of the code, the manufacturer’s
installation instructions, and all other relevant code requirements. All such material must be verified by grade
stamp, supplier receipt or other approved methods prior to final approval by the field building inspector.
Note that the deck substructure (supporting structure) below the wood decking surface may be constructed
with non-fire-treated lumber but must be preservative-treated to comply with CBC 2303.1.9.
Note also that SFBC 1511.10 #1 requires that the roof decks be less than 500 square feet in area. Hence,
the total area of all roof decks located on the same story shall not exceed 500 square feet.
07/24/2024
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Patrick O’Riordan, C.B.O., Date
Director
Department of Building Inspection
This Information Sheet is subject to modification at any time. For the most current version,
visit our website at sfdbi.org
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Technical Services Division
49 South Van Ness Avenue, Suite 500 – San Francisco, CA 94103
(628) 652-3720 – sfdbi.org
