Ceiling Pockets

[bmlxd40]

We have a couple rooms that have multiple pockets in the concrete structure as shown in the attached photo. We requested that the owner install a lay-in, tile ceiling in the room to avoid sprinklers in every pocket. The owner declined the ceiling stating that all the exceptions in NFPA 13 8.6.7.2 are met. This leaves us installing sprinklers under the narrow strip of concrete between the pockets.

This is a limited area sprinkler system supplied from a domestic water source. There simply isn't enough water available to provide a sprinkler in every pocket.

Sometimes I cant see the forest for the trees, and I miss the obvious, but this just doesn't seem right.

Thoughts?

 

[MatthewJWillis]

Would 8.6.4.1.2 (5)
Help you any?

R/
Matt

 

[SprinklerDesigner2]

It is not concrete T construction as I recognize it.

It appears the pockets are more than 22" deep which, just in my opinion, would require a sprinkler in every pocket. Just by looking I would guess pocket depth is 30" to 36".

I will assume, and it certainly looks it, that the room is OH but on chance is it light hazard? I say light hazard because if it is a non-combustible crawl space without storage that is exactly what it would be. If it is light hazard you could possibly make it work with small orifice sprinklers but maybe not.

 

[stookeyfpe]

It sounds like your applying the IFC limited area sprinkler provisions under the 2012 or earlier edition. That was a very screwed up code provision and it was changed in the 2015 edition to prohibit conditions like this.

With that said, this is noncombustible space so why are sprinklers required, as asked by MatthewJWillis?

 

[bmlxd40]

This room is a storage room. The primary code on this project is NFPA 130 which states sprinklers are to be provided in storage & trash rooms and a couple other areas. The pockets are 30" deep, so it meets item #2 in NFPA 13 8.6.7.2. To the best of my knowledge, it does indeed meet the all the requirements of 8.6.7.2, but that doesn't make me feel any better about sprinklers under that narrow strip of concrete with 30" deep pockets through the entire room.

 

[SherifBadran]

My view is that what you have is not a ceiling pocket and thus 8.6.7.2 should not be applied.

In NFPA 3.3.4, Ceiling Pocket is defined as " An architectural ceiling feature that consists of a bounded area of ceiling located at a higher elevation than the attached lower ceiling."

In addition A3.3.4 clearly states that "It is not the intent of this definition to be applied to structural and/or framing members otherwise used to define obstructed or unobstructed construction."

Also, you say you comply with 8.6.7.2 but I wonder is you comply with point (3) where the floor is protected by sprinklers at the lower ceiling elevation

As far as I can tell, there is no lower ceiling ! And what you have is really an obstructed ceiling construction. I believe the clause regarding ceiling pockets is intended for ceiling recesses similar to skylights where the whole area is protected under the lower ceiling and just that recess is allowed not to have sprinkler protection under the conditions listed in 8.6.7.2

My concern is sprinkler activation will be delayed relatively due to the lack of ceiling below the "pockets" and due to the depth and size of the "pockets".

Kind Regards,
Sherif Badran

 

[MGXFP]

This is a waffle slab. It isn't explicitly addressed in 13 like concrete tees. I'm afraid the obstructed construction rules may not apply in this case. The best bet is to have them put in a ceiling like you said. Other than that consulting the local AHJ would be where I would go in this case.

 

[cdafd]

Bmixd

So how many total sq ft is this room??

Or does it happen in multiple rooms??

 

[bmlxd40]

The largest of the two rooms is roughly 150 sq ft. The entire facility is built with this waffle type structure, but we are only protecting a handful of rooms. I have sent a letter to the AHJ and am awaiting their thoughts, but I still appreciate the responses regardless.

 

[cdafd]

Reading back through the posts it looks like you agree it meets 8.6.7.2

Not a designer

So six to seven heads in a normal room?

Fire starts, maybe some delay, but meets 13, plus small enough room should get hot fast.

If legal with 36 inch pocket than legal with 30