Todays inspection had a built in garage. The ceiling adjacent to the living area had drywall but the walls adjacent to the crawl space under the house had plywood rather than drywall. Do you need fire separation between the garage and the underfloor crawl space?

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"Some people are like slinkies. They serve absolutely no useful purpose. But still put a smile on your face when pushed down a flight of stairs."

Fritz,

I'm not quite understanding what you are describing.

Are you describing a house on a crawl space, with an attached garage, with the garage lower than the house - of course the garage would be lower than a house raised up on a crawl space - and the garage wall to the house and the garage ceiling are gypsum board, but ... where the garage wall extends down below the house level and the crawl space is on the back side of the wall - that area in the garage is plywood?

If so, yes, that entire wall between the house and the garage is required to have at least 1/2" gypsum board separating it from the house, or an equivalent ... an equivalent would be fire retardant treated wood panels rated for at least a 1 hour rating (the 1 hour minimum rating is not specifically addressed in the code, however, I am sure most AHJ would consider it as providing "equivalent" protection as the 1/2' gypsum board).

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
www.AskCodeMan.com

Yes, the garage is essentially a walk out partial basement. The only surface adjacent to a living area is the ceiling. There are 2 walls adjacent to crawl space but not living area. The question is about those 2 walls.
house.jpg

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"Some people are like slinkies. They serve absolutely no useful purpose. But still put a smile on your face when pushed down a flight of stairs."

But ... on the other side of the garage walls is the crawl space to the structure which supports the living space, right?

- R309.2 Separation required. The garage shall be separated from the residence and its attic area by not less than 1/2-inch (12.7 mm) gypsum board applied to the garage side. Garages beneath habitable rooms shall be separated from all habitable rooms above by not less than 5/8-inch (15.9 mm) Type X gypsum board or equivalent. Where the separation is a floor-ceiling assembly, the structure supporting the separation shall also be protected by not less than 1/2-inch (12.7 mm) gypsum board or equivalent. Garages located less than 3 feet (914 mm) from a dwelling unit on the same lot shall be protected with not less than 1/2-inch (12.7 mm) gypsum board applied to the interior side of exterior walls that are within this area. Openings in these walls shall be regulated by Section R309.1. This provision does not apply to garage walls that are perpendicular to the adjacent dwelling unit wall.

The way I am reading that is that those 2 walls to the crawl space, which is exposed to the residence, need 1/2" gypsum for two reasons: 1) the first highlighted-with-bold-section because the residence (and its structure) is exposed on the other side; 2) the second highlighted-with-bold-section because the garage is "below" - while it may not be directly "underneath" - the living structure and "the structure supporting the separation" "shall also be protected by not less than".

Not well written to be clearly define for your condition, however, I believe "the intent of the code" covers it, and everyone acknowledges that the code cannot specifically address every conceivable design.

In fact, after looking at your photo (which I did not see the first time?) that code section absolutely address that BECAUSE the structure is supporting the living space above the garage.

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
www.AskCodeMan.com

Thanks, I added the photo later. It looked wrong to me, I will write it up.

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"Some people are like slinkies. They serve absolutely no useful purpose. But still put a smile on your face when pushed down a flight of stairs."

Fritz,

With the photo, it fits the part highlighted in bold red text perfectly because the crawl space framing is structurally supporting the the separation walls and structurally supporting the separation ceiling to the living space above.

- R309.2 Separation required. The garage shall be separated from the residence and its attic area by not less than 1/2-inch (12.7 mm) gypsum board applied to the garage side. Garages beneath habitable rooms shall be separated from all habitable rooms above by not less than 5/8-inch (15.9 mm) Type X gypsum board or equivalent. Where the separation is a floor-ceiling assembly, the structure supporting the separation shall also be protected by not less than 1/2-inch (12.7 mm) gypsum board or equivalent. Garages located less than 3 feet (914 mm) from a dwelling unit on the same lot shall be protected with not less than 1/2-inch (12.7 mm) gypsum board applied to the interior side of exterior walls that are within this area. Openings in these walls shall be regulated by Section R309.1. This provision does not apply to garage walls that are perpendicular to the adjacent dwelling unit wall.

__________________
Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
www.AskCodeMan.com