Something's awry here. Can I assume that this garage is in close proximity (3' or less) to the property line or another structure, such as the house? That is the only reason that a true firewall would be required in a single family residential application.
If it is an attached garage and it isn't in close proximity to a neighboring structure or the property line, the inspector is dead wrong. On your average home a garage "firewall" is not required. A fire membrane is required, but there's a big difference. A true firewall is rocked on both sides of the studs. The code requires garages walls to be rocked with 1/2" and the ceiling with 5/8" if there is habitable structure above the garage. All supporting structure must be rocked on the inside. Rock on the outside is not a requirement.
If the structure is closer than 3' to the house, another building, or closer than 3' to the property line then the inspector is correct. Soffits with a 4" or less projection are not measured, but soffits that project more than 4" are where the measurement to the lot line should be taken.
Reference the IRC code section R302, Location on lot.
If it is an attached garage and it isn't in close proximity to a neighboring structure or the property line, the inspector is dead wrong. On your average home a garage "firewall" is not required. A fire membrane is required, but there's a big difference. A true firewall is rocked on both sides of the studs. The code requires garages walls to be rocked with 1/2" and the ceiling with 5/8" if there is habitable structure above the garage. All supporting structure must be rocked on the inside. Rock on the outside is not a requirement.
If the structure is closer than 3' to the house, another building, or closer than 3' to the property line then the inspector is correct. Soffits with a 4" or less projection are not measured, but soffits that project more than 4" are where the measurement to the lot line should be taken.
Reference the IRC code section R302, Location on lot.
