Sprinklers Req'd Above Ceilings With Openings?

11/27/2019

Got a question regarding sprinkler protection above hung ceilings. NFPA-13 states that sprinkler protection is NOT required above hung ceilings if the area above has non-combustibles even with small openings in the ceiling.

However, I seem to recall a requirement that if there are large openings in the hung ceiling, sprinklers are required above the ceiling, but only for a certain distance in from the edge of the opening.

Thoughts on what section provides that distance?

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6 Comments

Randy

11/27/2019 10:03:40 am

If you have large gaps, it may be a cloud ceiling. Check those requirements.

zack

9/30/2020 07:50:29 am

Wooden rafter , the space between each others is 26 cm, i have sprinklers above them

Matt

11/27/2019 10:12:45 am

Sounds like you're thinking of "Extension of sprinkler system above drop ceiling" - check out 8.15.23.3, and by association, Figure A8.15.23.3

11/27/2019 10:31:58 am

For sprinklers above ceilings with noncombustible construction:
First check if your openings are considered a ceiling with small openings per 3.3.21 and if the combined openings exceed the 20% stipulation per 8.15.1.2.

Then check if your openings are considered cloud ceilings per 3.3.5.1 because that's its own situation. If its not a cloud and not considered small openings, refer to 8.15.23.

The distance you're looking for is 0.6 times the square root of the remote area per 8.15.23.3 which has to be at least 24ft into the ceiling per 8.15.21.3.1

Appendix has additional content on all of these sections.

Franck

11/27/2019 01:05:05 pm

Maybe you are thinking of the paragraph with open gratings (8.5.5.3.4 and annex in the 2016 Edition), which states that sprinklers should be provided below open gratings and should be provided with shields, Then there is a requirement for the position of the shield. The purpose of that is that the heat will go through the openings and collect first above the open gratings, therefore, sprinklers are required above the « ceilings with a lot of holes » as the sprinklers located below the ceiling will not operate quickly. But because of possible obstruction to the sprinkler discharge pattern from the open gratings’ sprinklers are also required underneath. And a shield is mandatory to avoid water cooling of the fusible element from the operating sprinklers above.

You can also have a look to 8.15.14 for open grid ceilings.
Thus list the possible situations where you can have the sprinklers at the ceiling level only, and not below the open grid ceiling.
You have a minimum clearance between the sprinkler defkector at the ceiling level and the upoer surface of the open grid ceiling, that depends on the sprinkler spacing and occupancy classification.

Franck

11/27/2019 01:09:10 pm

This means that it is the other way round compared to your question.
It is not « when you need to provide sprinklers above the ceiling », but « when it is necessary to add sprinklers below the ceiling because of the water distribution pattern problems ».

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