crawlspace to garage fire seperation

[Bruce King]

I saw a garage the other day that only had one layer of 1/2 inch regular drywall between the lower garage walls to the underfloor crawlspace. I wrote it up without caring about how the actual code is written since I feel it is a safety issue. Typically there will be a foundation wall seperating these but this house had some interesting cost saving methods to say the least.

Does the IRC only mention garage to living space/attic or does it include garage to underfloor crawlspace too?

[Darren Miller]

Bruce;

I would look at it this way.
The code requires any wall that is supporting a fire 'rated' wall (in this case a fire separation wall) must have at least the same rating as the wall it's supporting.

[Jerry Peck]

Does the IRC only mention garage to living space/attic or does it include garage to underfloor crawlspace too?

The IRC states:
- 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.
- - "The residence" could be (should be) taken as meaning 'the structure' and not just the 'living space' within that structure. As the crawlspace is under the residence (the structure), any fire or similar occurrence in the crawlspace will affect whatever is above it (the residence).
- - And the protection is one layer of 1/2" gypsum board "on the garage side".

The IRC further states:
- 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.
- - Being as the garage is communicating with the crawlspace which is "beneath habitable rooms", I would say that 5/8" Type X would be needed at and below the floor level of "the residence". Above the floor level, go 1/2" the rest of the way up, or, just use 5/8" Type X all the way.

[Rick Cantrell]

had one layer of 1/2 inch regular drywall between the lower garage walls to the underfloor crawlspace.

From the 2006 IRC
R309.2 Separation required. The garage shall be separated
fromthe residence and its attic area by not less than 1/2-inch (12.7
mm) gypsum board applied to the garage side.

What is the problem?

[H.G. Watson, Sr.]

Is the subject a single family free standing home with attached garage?
A two-family dwelling?
A row home/townhome?
A multi-family dwelling (such as a condo, a quad, a triplex, etc.?)

What is present in the "crawlspace" (mechanicals? electrical system panels? sump pumps? plumbing appliances? storage?, HVAC ducting, equipment?, etc.)

Is the crawl space part of the thermal envelope of the home?

The separation wall has requirements beyond its function as a garage to living space separation. Insulation, structural, bearing, etc.

What type of foundation system for the crawlspace and the home above?

Is the residence in a flood/surge zone?

[Bruce King]

From the 2006 IRC
R309.2 Separation required. The garage shall be separated
fromthe residence and its attic area by not less than 1/2-inch (12.7
mm) gypsum board applied to the garage side.

What is the problem?


Since the interior already has drywall you end up with 2 layers for garage to house seperation. I see no reason not to have a two layer seperation to the crawlspace combustibles. But hey, who would want drywall facing a typical vented and humid crawlspace in a new house. This house also had gaps all along the lower edges where carbon monoxide would enter the crawlspace and had that one layer of drywall touching masonry in places.

[Jerry Peck]

Since the interior already has drywall you end up with 2 layers for garage to house seperation.

An incorrect statement.

You end up with one layer on each side. You do not count the layer on the other side of the wall as the framing is already exposed to the fire by the time you get to even think about considering the interior drywall. ;)


I see no reason not to have a two layer seperation to the crawlspace combustibles.

There is no reason to have two layers - both layers would be on the same side of the wall and the layers would have staggered joints. Depending on how that was constructed (two layers, both sides, staggered joints, proper screw patterns, etc. - and it is the "etc." which gets you ;) ) and you have a 2-hour rated wall.

[Gary Bottomley]

I saw a garage the other day that only had one layer of 1/2 inch regular drywall between the lower garage walls to the underfloor crawlspace. I wrote it up without caring about how the actual code is written since I feel it is a safety issue. Typically there will be a foundation wall seperating these but this house had some interesting cost saving methods to say the least.

Does the IRC only mention garage to living space/attic or does it include garage to underfloor crawlspace too?

I would have to assume that the floor surface of the garage, being sound enough to withstand the weight of and weather-ability requirements of normal garage floors would be an equivalent fire separation (no fire wall required) as 1/2" drywall, meeting the intend of the code. What is this structural element Bruce?

[Ron Keeney]

The trick to that is realizing that the IRC wants a "fire separation" between a garage and the rest of the house -- NOT a true "fire-rated assembly" or "fire-wall". Those three are very different "animals" within the Code.

And the Code changes in recognition of reality: 12 years ago, one had to have the garage floor stepped 4" down from the house floor -- all to prevent carbon monoxide (heavier than air) or even spilled gasoline from getting into the house. But since concrete garage floor are normally constructed with a slope away from the house (and out under the garage door) for simple drainage of rain water off a wet car, those potentially hazardous conditions never lead to a problem, and that 4" step got eliminated in favor of easier HC accessibility and the elimination of the stumbling hazard.

[John Benson]

I saw a garage the other day that only had one layer of 1/2 inch regular drywall between the lower garage walls to the underfloor crawlspace. I wrote it up without caring about how the actual code is written since I feel it is a safety issue. Typically there will be a foundation wall seperating these but this house had some interesting cost saving methods to say the least.

Does the IRC only mention garage to living space/attic or does it include garage to underfloor crawlspace too?

One layer of 1/2" sheetrock is the required separation at the common wall between the garage and the residence. It is required on the garage side. It's not a rated assembly or a fire wall or anything else. 5/8" type x is required on the ceilings where the garage is below living space. If the area above the garage is storage 1/2" is acceptable. To your question I am assuming there are steps going up from the garage(concrete floor) which is the top of the masonry foundation, to the floor level of the residence. At the common/ separation wall there is the wood framed band, or a floor truss that is above garage floor level and below residence floor deck level that is running under the framed common wall. So you are saying the only thing covering the truss or wood band or I-joist is 1/2" gypsum on one side, separating the garage from the crawl space. That is acceptable by 2006 IRC.

[Jerry Peck]

The trick to that is realizing that the IRC wants a "fire separation" between a garage and the rest of the house ...

Not really.

The IRC goes out of its way to *not* use the term "fire" separation and to only use the term "separation", as such all the IRC wants is "separation" ... yeah, yeah, we all "know" what the IRC *is not* saying and what you are saying ... ;) ... but you should not be saying "fire" with "separation" for the IRC. :)

[Gary Bottomley]

Not really.

The IRC goes out of its way to *not* use the term "fire" separation and to only use the term "separation", as such all the IRC wants is "separation" ... yeah, yeah, we all "know" what the IRC *is not* saying and what you are saying ... ;) ... but you should not be saying "fire" with "separation" for the IRC. :)

I have also wondered about the rather loose wording of this section saying 1/2" gypsum applied to the garage side. Could one assume they don't care about attachment method or even if the joints and seams are taped?

[Jerry Peck]

I have also wondered about the rather loose wording of this section saying 1/2" gypsum applied to the garage side. Could one assume they don't care about attachment method or even if the joints and seams are taped?

The gypsum board needs to be attached properly (nail/screw length and spacing) and the joints need to be taped and finished (well, not a Level 5 finish, but you know what I mean ;) ... 'taped and mudded' ... 'finished' is a bit strong of a term)