13R system what constitutes a non combustible stairwell?

[SprinklerDesigner2]

The architect of record confirmed to me, in writing, that the fire sprinkler system called for is 13R so I'm covered there.

It's your typical four story motel constructed of wood studs plywood wood trusses pretty much what we see every day.

But the stairwells themselves are a little bit different there's wood studs and two layers of 5/8 drywall but the stairs themselves are constructed of concrete and steel nothing combustible.

On past projects I've always sprinklers underneath the landings and inside the stairwells because the stairs were combustible or made of wood.

I am not sure what to do here, my gut feeling is to sprinkle the entire stairway at each floor level and under each landing, but is that required or can I get away with just top of the stairwell and underneath the bottom landing?

 

[stookeyfpe]

As far as NFPA 13R is concerned your shaft is noncombustible because the stair are erected from noncombustible materials and the shaftway is constructed where at least 2 layers of fire-resistance rated gypsum wall board erected with staggered joints and fastener placement creates an enclosure of noncombustible materials. The use of wood as a framing material has no bearing on the NFPA 13R sprinkler requirements.

 

[SprinklerDesigner2]

Thank you Stookey,

Running into this, steel stairs with type III construction, was a new one for me.