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sheet rock for firewall in a garage

10940 Views 4 Replies 2 Participants Last post by  Termite
I am looking for guidance for a bit of a mess. My daughter built a garage and followed all codes as far as she could tell. Electrical passed just fine. First structural inspection also okay. The final structural inspection raised a HUGE problem. She was planning on putting the sheetrock/firewall materials inside the garage. The inspector says that it must be both inside and also under the (already installed) siding and sofit on the outside as well. Would two layers of inside be equivalent to adding a layer under the siding on the outside? Are there other ways to fix this problem?

Thanks much,
Sandy F.
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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.
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Yup, walls and eave projections parallel to the lot line have to be fire rated when they're that close. Unfortunate, but better than catching it at the very end of the project!
One thing you should determine from the inspector is whether he'll require fire retardant treated plywood for the roof sheathing on the portion of the roof that must be fire rated. He seems to be pretty spot-on with requiring the soffit be pre-rocked, but the roof deck must also be fire treated at leat 4' back in a lot of cases. Otherwise rocking the soffit is a big waste of time.
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