Omit Sprinkler from 4' x 6' x 5' Skylight in Pocket?

3/12/2021

I have a skylight that is 4-ft (length) x 6-ft (width) x 5-ft (depth). The room has a drywall ceiling and the depth of the pocket is about 4-ft of dry wall between the ceiling with an additional 1'-0" of glass (for the skylight) that domes above the roof at the top of the pocket.

Can I omit a sprinkler in the skylight per NFPA 13 2016 Section 8.5.7, or do I need a sprinkler in the skylight under Section 8.6.7 due to the depth of the unprotected ceiling pocket exceeding 36-inches?

NFPA 13, 2016 Section 8.5.7 (Skylights) permits sprinklers to be omitted from skylights not exceeding 32ft² that are separated by at least 10ft horizontally from any other unprotected skylight or unprotected ceiling pocket.

NFPA 13, 2016 Section 8.6.7 (Ceiling Pockets) says sprinklers shall not be required in ceiling pockets where all of the following are met: (1) The total volume of unprotected ceiling pocket does not exceed 1000ft³.(2) The depth of the unprotected ceiling pocket does not exceed 36 in. (3) The entire floor under the unprotected ceiling pocket is protected by sprinklers at the lower ceiling elevation. (4) the total size of all unprotected ceiling pockets in the same compartment with in 10ft of each other does not exceed 1000ft³. (5) The unprotected ceiling pocket has noncombustible or limited-combustible finishes. (6) Quick-response sprinklers are utilized throughout the compartment.

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9 Comments

Mike

3/12/2021 09:20:23 am

According to the 36" requirement, yes.

Bill

3/12/2021 09:23:33 am

Section 8.5.7 would apply since the skylight is less than 32 sq ft. The standard is silent on the depth. The concern over heat collecting in the skylight was resolved by limiting the size and requiring the minimum separation of 10' from any other skylights or unprotected ceiling pockets. Skylights greater than 32 sq ft would be required to comply with 8.6.7.

DANIEL ACOSTA

3/12/2021 09:23:42 am

I would say yes, it does require a head because it does not meet all the criteria for 8.6.7. Specifically, the second requirement of <36" in depth and 8.6.7 states that ALL requirements must be met to omit sprinklers in skylights.

3/12/2021 09:39:30 am

After re-reading the NFPA 13 handbook, I'll change my answer to no. You don't need a head in the skylight if it's the only one for the reasons that Bill and Colin explained.

Colin Lusher

3/12/2021 09:32:34 am

Sprinklers are NOT required in your skylight.

Bill is correct that section 8.5.7 does not have any depth or volume requirements. The only requirement is that it be smaller than 32 sq.ft.

The ceiling pocket rules do not apply to the skylight....the last paragraph of the ceiling pocket rules, section 8.6.7.2 confirms this: "Sprinklers shall not be required in skylights and similar pockets in accordance with 8.5.7."

Kelsey

3/12/2021 10:24:37 am

I agree with this. There is a separate skylight rule for a reason. No head would be required in this case.

Jesse

3/12/2021 10:38:37 am

Great question, because of the depth. However, its not a ceiling pocket, its a skylight. As such, 8.5.7 governs, not 8.6.7. Because 8.5.7 doesn't specify a max depth, and only specifies square footage and not volume you should be able to omit this sprinkler.

Munnawar Khan

3/21/2022 02:59:09 pm

So I'd like to propose a similar yet different scenario, where 8.5.7.1.1 states "when a sprinkler is installed directly beneath a skylight not exceeding 32 sq.ft., the distance to the ceiling shall be measured to the plane of the ceiling as if the skylight was not present". Two things I'm not understanding here: 1) "..sprinkler installed directly beneath..": does this mean a head in the opening, somewhere in the depth of the skylight, from the finished ceiling up to the clear glass? 2) "..as if the skylight was not present." : the way I'm interpreting this is the distance from where the sprinkler is installed (the deflector) at the lower ceiling level - or we could say at the ceiling level where the skylight opening is - can be measure as if the skylight isn't there, meaning the deflector should be placed a min. 1" down from the opening, even if from the opening to the skylight glass is say 5 feet?
If that is the case where if a head is installed in this manner (so as to ignore the depth of the skylight) then here's one last proposal/query: a bulkhead is installed at a lower elevation than this ceiling level. And so now are we able to implement ceiling pocket requirements? The total volume of ceiling pockets is less than 1000 cu.ft. in the compartment, and with the other requirements fulfilled from 8.6.7.2 we'd be able to get away with heads only in the the lower bulkhead ceiling. My issue with this though is the presence of the skylights. Hoping someone can help me out here. Thank you.

Jeffrey Davis

3/7/2023 09:32:32 am

Now what if this was an FM Global project? FM Global, Installation Guideline for Automatic Sprinklers 2-0 does not mention any allowance for omission of protection for this scenario. Is protection in skylights required per FM Global regardless of skylight dimensions or orientations within the space?

Omit Sprinkler from 4' x 6' x 5' Skylight in Pocket?

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