Sprinkler below roof

[Sam9461]

Hi Guys,
Can someone give me some guidence?
An existing 1 story warehouse is being converted into a chemistry lab. The space is currently sprinklered it is clear from finished floor to underside of roof deck,approx 14'. The building is heavy timber frame, masonry and stucco, the roof is wood joist and precast concrete (flat). The new lab lay-out incorporates a drop-lay-in accoustical tile ceiling 9' above finished floor.
My question; Can I remove the existing sprinklers which are installed approx 13'above the floor, reroute & extend
pipe and install new ones at the new ceiling? The way interperet NFPA 13 Chapter 8 I think I can, but I'm uncertain.
Any input or comments would be of help.
Thank You.
Sam

 

[TravisMack]

From your description, it sounds like you have a combustible space (wood) above the ceiling. Therefore, the sprinklers above the ceiling are going to be required to stay. You will simply need to attach to the branch lines with 1" snap-lets (or similar) and pipe to the new head locations. Just a typical tenant improvement.

 

[PEDARRIN2]

NFPA requires that when you make such adjustments, that you must show that the revised system will work with hydraulic calculations.

In effect, you will have twice the coverage required i.e. you will be sprinklering above the ceiling and below the ceiling. The system may not be sized for both. The hydraulic calculations will determine it.

 

[TravisMack]

pedarrin2,

You are correct. I was making assumptions that the original system was probably designed to OH Grp II at a minimum, and that the lab would be OH Grp II. With the use of QR sprinklers, the lab design area would be reduced to 900 sq ft, so in theory, it should work without a problem. However, you would need to calculate it to prove it. But, I don't think I have ever done one with this type of scenario that didn't work.

 

[Sam9461]

Thank you for your responses to my question. They were of great help.
Sam