Overhead door coverage.

[ContractorDave]

As noted elsewhere, I have a client that is installing an overhead door in a warehouse. it's 8'w x 10'h so 8.5.5.3.1 of course applies. But there was a question posed and then another hypothetical one was asked somewhat in jest - but in reality it's actually quite valid:

The door as I said is 10' high. But the T-bar ceiling is another 8' above that, so I'll have an 8' drop more or less, and rather inconveniently, hanging in mid air when the door is closed (though it will be afforded some protection by the door rails). Does it matter the distance from the ceiling to the top of the door? NFPA 13 doesn't say.

The hypothetical question in jest was how low to the floor can the door be before it doesn't require coverage beneath it? The real life equivalent of this is large ductwork in a mechanical room that is sometimes only several inches to a few feet off the floor but may be well over the 4' width. NFPA 13 doesn't address this either.

Maybe I'll need that engineer after all

Regards
Dave

 

[cdafd]

Maybe when you cannot store under it???

Two feet??? 3. 4. 5?????

 

[b1ueshift]

If a duct is 12" off the floor, there doesn't seem to be any point in putting a sprinkler under it.

In my humble opinion, overhead services need to be installed 7' above the floor - anything below that is room contents. You wouldn't normally install sprinklers below a bench or counter top, but I think you should if they were 7' above the floor.

 

[skdesigner]

8.5.5.3.1 Sprinklers shall be installed under fixed obstructions over 4' wide such as ducts, decks, open grate flooring, cutting tables and overhead doors.

Don't know boys, it seems pretty cut and dried to me. I've had to drop sprinks below tin just off the floor, ditto with cutting tables. Assigning an arbitrary elevation and saying...abracadabra! everything below this level is inherently safe, because to sprinkle under it just doesn't make sense...could get a guy into some sticky situations.

my two cents

 

[chevy4x4trucks]

The only omission that NFPA 13 allows as far as distance from one surface to another is the 6" for a ceiling below solid wood members. That's where I have made the cut off point when it comes to putting heads under low fixed obstructions.

I know it's a different code reference, but the same reasoning would apply since sprinklers wouldn't be able to develop any type of a spray pattern being so close to the ground.

 

[NJ1]

I recommend having an Engineer to evaluate any system when installing 5 sprinkler heads or more. Anything other than that a license holder should be able to figure that out.
Than again many things play a big role such as main size, water pressure, branch size, obstructions, etc.
All this must be analyze by a license P.E.