Enclosure under interior stairways

[VLADIMIR LEVIN]

Can someone clarify section 1011.7.3 BCNYS.
I have a metal stair with a utility closet underneath it.
I think the closet walls need to be 1 hour, and the underside of the stair needs to be 1 hour?

 

[Mr. Inspector]

IBC 101.7.3 says the same thing but also requires it to be at lease the same fire -rated construction as the stairway encloser and the access to the enclosed space cannot be directly from within the stairway encloser.

 

[Yankee Chronicler]

Is the stair an enclosed exit stair, or is it an exit access stair?

 

[VLADIMIR LEVIN]

Is the stair an enclosed exit stair, or is it an exit access stair?

It's an exit access stair

 

[Yankee Chronicler]

1011.7.3 Enclosures Under Interior Stairways​

The walls and soffits within enclosed usable spaces under enclosed and unenclosed stairways shall be protected by 1-hour fire-resistance-rated construction or the fire-resistance rating of the stairway enclosure, whichever is greater. Access to the enclosed space shall not be directly from within the stairway enclosure.

The language seems clear. If the space beneath the stair is enclosed and used as a closet, the enclosure has to be one-hour rated, including the soffit (the celing of the closet).

I agree with your opening assessment.

 

[steveray]

The language seems clear. If the space beneath the stair is enclosed and used as a closet, the enclosure has to be one-hour rated, including the soffit (the celing of the closet).

I agree with your opening assessment.

And not accessed from the enclosure ....which this one has none...

 

[VLADIMIR LEVIN]

Can someone help me with a 1h assemble for under the stair.
Is it simple a 1H rated sloped ceiling?

 

[JPohling]

Typically we use a shaft wall assembly since you can only construct from one side

 

[VLADIMIR LEVIN]

Typically we use a shaft wall assembly since you can only construct from one side

the stair is above a closet. What about the underside of the stair?

 

[VLADIMIR LEVIN]

The language seems clear. If the space beneath the stair is enclosed and used as a closet, the enclosure has to be one-hour rated, including the soffit (the celing of the closet).

I agree with your opening assessment.

Do you know a UL assembly for the underside of the stair, or can i just spray it with intumescent paint?

 

[Yankee Chronicler]

the stair is above a closet. What about the underside of the stair?

Use 1-hour shaftwall in a [sloped] horizontal application.

Spray-applied fire-resistant materials provide a rating for structural members as structural members, they do not provide rated fire-separation assembles.

 

[Paul Sweet]

If you have 2 by stringers you can use Gypsum Association FC 5406. It requires 2 layers of 5/8" Type X gypsum board, and the ceiling provides 1 hour protection for the joists. FC 5407 & FC 5408 are the same, except for I-joists or trusses.