Sprinklers Required within Each Beam Pocket?

7/22/2022

I have 30-inch deep beams which are spaced just under 5'-0" apart running east to west.

I have 48-inch deep beams running north and south spaced 24'-0" apart.

Do I have to get a row of sprinklers in every 5-foot pocket?

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7 Comments

Anthony

7/22/2022 07:15:42 am

Yes you do need to be in every pocket.

This is clearly obstructed construction that calls for pocket protection. You cannot center a sprinkler and spray under ( see fig 8.6.5.1.2(a) and table 8.6.5.1.2)

HOWEVER! You're just 1/2'' shy of spacing at 2-6'' from the edge of an obstruction to allow a deflector above by 7.5.'' So dig a little and see if there will be any fire proofing or insulation will be placed on the bottom of the deck. if that insulation is 1/2'' thick you're good to go as long as its not fire proofing in to the bottom of the beam as well ( extending that beam as well as the deck depth). This will only work at the 30'' beams.

Remember the lip of the beam is an obstruction not just the vertical member its unclear if you're taking that into account.

Also if this is a new build see if the GC is willing to burn holes at the middle 1/3rd of the beams for you to hang and rout pipe through. It may help with coordination and you can use that as a hanger. Note this will require shorter pipe lengths to physically get the pipe into the beam pocket.

Alex

7/22/2022 08:52:42 am

Hi,

8.8.4.1.2 states that you are allowed to install the sprinklers with the deflector 22 inches below the deck for obstructed construction. Then, Anthony is correct, you are only off by 1/2".

Note, if there is no insulation or material in the pockets and you DO need to provide heads in each, 8.8.4.1.2(3) states that the deflectors need to be 12 inches below the ceiling.

Alex

Dan Wilder

7/22/2022 08:39:08 am

Not knowing what the hazard classification is or the bottom flange width...
Couldn't you space a sprinkler 3' from one beam and 22" down in the pocket, skip a bay, and provide a sprinkler in the third pocket 3' from beam, then repeat?

| 3'-> | skip | <-3' | 3'-> | skip | <-3'

However, just a quick layout for 10 bays (50') shows the following (assuming a 130ft², if you can go 225 the bay skip is the better option):

Sprinkler with bay skip (225ft² only)
14 sprinklers with 100' of pipe

Sprinkler in every pocket (130ft²)
20 sprinklers with 100' of pipe

Sprinkler bay skip (130ft²)
21 sprinklers with 150' of pipe

Barry

7/22/2022 09:13:09 am

If these are concrete beams, Is it possible the beams actually meet the NFPA 13 Definition of concrete tee construction?

Jesse

7/22/2022 09:27:51 am

Would love to know a little more. Wooden beams? Concrete?

danefre

7/22/2022 10:20:46 am

A lot of variables here...

Assuming you're designing for 130sqft and the building doesn't have a ton of these 24'-0 bays then running perpendicular to W30 with branchlines 12'-0 apart and heads 5'-0 OC in every pocket is your best option.

Also, assuming this is beam & girder or panel construction with no unfilled penetrations.

Skipping is not in the cards as you would be exceeding 130sqft. Plus you would need to be 3'-2 or 3'-3 away from the center of the beam. Adding a 3rd branchline in every bay is not cost effective.

Mickey Rowe

12/27/2022 12:27:39 pm

I have obstructed solid 18" steel beams with pockets being over 320 sq foot. The area is OH Grp 2 warehouse. Can I space my lines 14 ft apart if protecting every pocket.

The beams are 10 ft on center. .Sprinkler head is 5ft center off beam and 14ft to the next branchline

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Sprinklers Required within Each Beam Pocket?

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