Sprinklers Below Open Stairs

[FireFreak08]

I have a project with an Internal Stair (non-egress). It goes from the 1st to 2nd floor. The risers/treads are the only solid surface, it will be open to a water feature below the stair so there is a non-walkable space below the stair. What are the requirements for this? Are sprinklers required? Does material (combustible/vs non-combustible) treads/risers make a difference? I'm thinking I do not need to add sprinklers but not quite sure. NFPA 13, 2007 doesn't seem to address this specifically. I can only place together different sections and make a judgement call.

Any advice/tips would be greatly appreciated.

 

[cdafd]

Normally as an ahj I require them under protection to be provided under solid stairs

Depends on the length and width sometimes,

8.10.6.3.2. 2010 edition and 8.10.7.3.2

 

[FC12]

You could also use the 4' wide obstruction rule....8.5.5.3.1 in NFPA 13 2010 ed.

 

[MGXFP]

I usually add them; especially if the tenant can use beneath the stair for storage.

 

[stookeyfpe]

The Section 8.15.3 requirements for combustible and noncombustible stairs was clarified in the 2010 edition of NFPA 13. You should find your answer in this section.