Thermo Ambara tongue-and-groove Nickel Gap/Reverse siding
This is a listed siding assembly. Listing 8140-2377:0003. This site cites OSFM BML. Match the model and orientation.
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Thermo Ambara tongue-and-groove Nickel Gap/Reverse siding is listed by CAL FIRE for wildfire-area use as a defined wall assembly.
For the base profile, listing 8140-2377:0003 requires at least nominal 1 × 6-inch siding. It goes horizontally over 7/16-inch exterior OSB, supported by nominal 2 × 4 wood studs at 16 inches on center. The same listing includes named WWPA and Redwood pattern alternatives whose nominal sizes differ. Choose the pattern first, then match its size and construction to the complete listing instead of applying the base-profile dimensions to every alternative.
A live BML check on August 25, 2026 found Thermo Ambara listed, with expiration stated as June 30, 2027. Its live description names no test protocol. Confirm the applicable test standard, exact model, and current GOVmotus entry before specification.