Sprinkler Requirement in Concealed Space

[mss28]

I have a renovation and alteration school project where existing deck form is paper reinforced wire mesh (steeltex) placed over 16" deep steel joists. See attached. I presume this concrete form to be a combustible material. Upright sprinklers are provided in concealed ceiling cavity for most of the spaces. There is general music room above which an acoustical ceiling (consisting of 2 layers of gypsum and batt insulation) is attached to bottom of steel joists with isolation hangers. The ceiling covers all perimeters of the room. There is only sprinkler piping above this acoustical ceiling running through joist openings and interstitial space is below this acoustical ceiling. The contractor has already installed acoustical gypsum ceiling for the room. Fire marshal mentioned that the void between existing deck and acoustical ceiling requires sprinkler. Is there any way to avoid this? The ceiling has two layers of gypsum board extending perimeter walls. I am not really sure how the fire will start in this void space. Can you please advise?

Building is type IIB construction.

Thank you,

 

[steveray]

Take it down before you put the ceiling up or beg the FM for forgiveness.....Really he would probably have to cite a violation as it is an existing building I assume....ASSUMING you didn't make it worse it's as safe as it was before the construction...

 

[mss28]

There was not any upright sprinkler above ceiling in existing construction. This is a full renovation with 10,000 sf ft new addition. Only existing exterior walls, interior bearing walls, roof and structure were not demolished. I did not think that it would be an issue as we are covering combustible deck with gypsum ceiling assembly below joist.

 

[TheCommish]

Try NFPA 13

8.15.1.2.1* Concealed spaces of noncombustible and limited-combustible construction with minimal combustible loading having no access shall not require sprinkler protection.​

 

[Paul Sweet]

Could you spray it with an intumescent paint if it doesn't meet the definition of limited combustible? I don't think it should be more dangerous than drywall since it's thin paper with concrete adhered to it.

 

[steveray]

A reasonable AHJ would work with you to find an acceptable alternative as it was an existing (and theoretically approved) condition....Or ask for a mod from OSBI....

 

[mss28]

Could you spray it with an intumescent paint if it doesn't meet the definition of limited combustible? I don't think it should be more dangerous than drywall since it's thin paper with concrete adhered to it.

We have remove all ceiling assembly to apply intumescent paint. It is not feasible.

 

[steveray]

We have remove all ceiling assembly to apply intumescent paint. It is not feasible.

Can you say what Town?