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» ICC Bulletin Board » Code Chat » Building and Residential Codes -- Non-Structural Issues » IRC 309.2 Garage Separation

   
Author Topic: IRC 309.2 Garage Separation
kar108
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A garage is separated from a residence by 1/2" drywall on the wall separation; 1/2" drywall is applied to the bottom of the trusses to separate the garage from the uninhabitable attic space.

Are the walls supporting the trusses required to be protected by gypsum board?

(I read the code and commentary to require protection for the supporting walls only when there is a floor-ceiling assembly with habitable space above)

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kar108

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TwilightZone
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Correct in that the separation is only req'ed if there is living space on the other side of wall/ceiling. The ceiling should be 5/8" sheetrock or equivalent (not 1/2")
if separating living space above, and all structural members for the floor system need to be covered (walls, beams, combustibles posts)

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John Drobysh
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kar108 -

Fortunately for me, and the rest of us in NYS, New York State has taken out much of the guesswork:

§RR309.2 Separation required. The garage shall be separated from the residence and its attic area by horizontal or vertical separations conforming to §RR309.2.1 and §RR309.2.2.

§RR309.2.1 Vertical separations. Where partitions are used to separate vertically an attached garage from a dwelling or its attic, the partition assembly shall have a 3/4-hour fire-resistance rating.

EXCEPTION: In lieu of providing partitions that have a 3/4-hour fire-resistance rating, one layer of 5/8-inch-thick, Type-X, gypsum board
maybe installed on the garage side and one layer of 1/2-inch-thick, Type-X, gypsum board maybe installed on the opposite side. Application shall be in accordance with §RR702.3.

§RR309.2.2 Horizontal separations. Where horizontal construction is used to separate the garage from the residence or its attic, such
construction shall be protected with one layer of 5/8-inch-thick, Type-X, gypsum board, installed in accordance with the requirements of §RR805.1.
Openings in horizontal separations shall not be permitted except where the residence is otherwise protected by vertical separations. Where the
horizontal separation is a floor-ceiling assembly, the structure supporting the separation shall also be protected by not less than 5/8 inch (15.87 mm) Type-X gypsum board or equivalent.

Our reps at the ICC level have been trying to get these reqs into the IRC for two cycles now. Unfortunately, the Res sprinkler issue has clouded discussion on the subject... Why improve safety with compartmentalization when you can sprinkler instead? But, I digress...

Not having the unmodified Res Code provisions, I can only offer an opinion based on my experience (limited to NYS Codes). Yes, the supporting walls should be rocked. What good is the gyp board on the ceiling if the walls have no protection?

I am sure opinions will vary...

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FOREST
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kar 108,
Reading the code section 309 of the IRC the walls do not support a floor/ceiling assembly therefore it is not required to have 1/2" drywall.As for the 5/8" drywall on the ceiling the first sentence in 309.2 would indicate only 1/2" need be applied.

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nineiron
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Don't forget that other issues may exist in the walls that may require protection i.e. exposed electrical in the wall cavaties, etc.
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Weedenski
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This may be worthy of a separate thread, but I have a question about Section 309 also.

I my experience, as a contractor and now an inspector, I have run across the use of either 1. Heavy timber(8"x8") or large Glu-lam beams and collumns in garages.

My question is this: Are structural members of this size still required to be covered by drywall in a garage with living space above?

I understand the intent. but if a 2x6 wood wall with 1/2" gypsum on it will survive a fire long enough, wouldn't a large diameter beam or log collum also be permitted to be uncovered if it too could last long enough in a fire to meet the codes intent?

how does your jurisdiction deal with this problem? Covered, or uncovered, that is the question. Thoughts? ideas?

Thanks

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peach
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providing protection for the electrical can be achieved without using drywall.

A lot depends on how the electrician runs the conductor..

Those horizontal runs make a dandy rake holder..

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mtlogcabin
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Peach The orange and yellow wires will hold more weight than the white will [Big Grin]

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Builder bob
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weedenski- sure gluelam may work providing that the non-prescriptive design is certified by a strucutral engineer performing burn rate (char rates) of timber and providing documentation that the structural member will provide structural stability for the time required by the prescriptive means of the IRC. (about 15 to 30 minutes.)

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Weedenski
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Thanks Bob, that's what I was looking for.

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Will Design/Build for Food
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Note: As a longtime user of char calculations on exposed glulams, note that you need to specify 1 hour stamp on said beams. This involves a lamination layup with high quality tension laminations on both the soffit (bottom) lamination, as well as the next lamination up from the bottom. Thus, the bottom lam can burn or char away, and you still have the glulam equivalent of the "bottom flange" in place.

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