Is drywall needed under stairs?

10 years ago

Home inspector on house sale said "There is no drywall under basement stairway for fire stopping. This should be installed for improved safety." I'm trying to figure out what he means and whether code requires it.

First of all, we have no basement, only crawl space. The stairs go from the 1st floor to 2nd floor. Here's a photo.

There's a small door that goes under the stairs (from inside the coat closet, the door of which is on the far LH side of the above photo). From inside the stair cavity there are just studs, not drywall. On the other side of the stair wall is the kitchen, and we did cut a hole in the wall and recess the fridge under the stairs a few inches.

So is there really a code requirement that the inside/underside of the stairs need to be drywalled? I don't get how there's a fire hazard without it, given the open floorplan/staircase.

Any and all enlightenment appreciated.

Comments (8)

live_wire_oak
10 years ago
All interior wall surfaces of a home are required to be finished with a fire preventative surface. Drywall is just the cheapest option. Since your basement is not a "utility area" but a living area, it has to have drywall or another fire resistant surface on all walls. Including the space under the stairs.
weedyacres
Original Author
10 years ago
Thanks for following me over here, live wire. :-)

BTW, we have no basement, living or dead.

I did talk to the inspector after posting this, and he basically said that because there's a small door between the coat closet and under the stairs, the under stair area has to be drywalled. He said the alternative is to remove the small door. Then the under stairs area is no longer living area and need not be drywalled on the inside.

I think we'll offer to close up the entry point, but I'm not going to drywall that cavity.
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_sophiewheeler
10 years ago
I'm going to argue with you on this one. The refrigerator is recessed into an undrywalled cavity, so what happens if something goes kerblooey and you have a fire from the compressor or something. The space needs to be drywalled.
kirkhall
10 years ago
What refrigerator? I see a closet door.
renovator8
10 years ago
The main stair in a home is the only required path of egress from the second floor. If the space below it is an "enclosed accessible space" it must be protected with unrated 1/2" gypsum board.

The definition of "accessible" in the IRC is as follows: "access that requires the removal of an access panel or similar removable obstruction".

This minimal protection is intended to allow your family a short period of time to use the stairs in case of fire. In any other building type this exit would be required to be one of two enclosed and fire rated stairs.

Draft stopping of the staircase framing is a separate unrelated requirement intended to prevent the undetected spread of fire to an upper floor.
weedyacres
Original Author
10 years ago
Kirkhall: Fridge is on the other side of the wall, recessed under the stairwell.

Holly: you're correct, to meet code the back of the fridge recess would also need to be sealed off.

Renovator: Thanks for the code verbiage. That always aids understanding. Was that a typo when you said unrated 1/2" gypsum?
aidan_m
10 years ago
Unrated 1/2" gypsum is regular drywall. Rated drywall would refer to 5/8", which is fire rated for a 1 hour separation.
renovator8
10 years ago
Discussions about fire ratings can go off the rails quickly but I will try to clarify what the subject if anyone cares to understand it.

I should have said that the drywall required under a stair does not have to be "fire-resistant"; in other words, it doesn't have to carry a fire-resistance classification of Type X or Type C and can be ordinary drywall.

No material by itself is "fire-rated", only "assemblies" can be fire-rated (assemblies = fire walls, fire separation partitions and floor-ceiling assemblies).

"Type X" drywall is defined as fire-resistant drywall that when applied to each side of wood wall studs can remain intact after 1 hour of exposure to fire from one side and then a fire hose stream test. When that standard was developed, the drywall that would do that happened to be 5/8" thick so today 5/8" fire-resistant drywall is labeled as Type X.

Half inch thick fire-resistant drywall is labeled as Type C and can achieve fire-ratings of 1 to 3 hours in various assemblies as tested by UL and other agencies.

Fire-resistant drywall and regular drywall both resist fire by releasing large amounts of water vapor from the gypsum core when heated but fire-resistant drywall has fibers in it that allow it to still be intact longer and withstand a hose stream test thereby preventing hot gasses and flame from spreading to adjacent spaces for a longer period of time.

When Type X or C drywall is used on both sides of a wall or as a ceiling the resulting assembly can pass a test giving it a fire-resistance rating in minutes or hours.

The drywall required under a stair is not part of a tested assembly so it isn't fire-rated but it will protect the stair of a home long enough for the occupants to escape.

Since the inspector did not mention the hole for the refrigerator he probably did not see it. If the refrigerator actually penetrates the wall under the stair, a wall must be installed behind it. As has already been pointed out this is a serious hazard to egress.

This post was edited by Renovator8 on Thu, Aug 1, 13 at 16:16