Great question. So without mention of applicable edition, I'm referencing 2016 (personal preference, because I don't want to learn the new format of 2019 yet....lol).
It appears as if it is the intent of the committee to allow omission of sprinklers at skylights for both uprights, pendents, AND sidewalls since the skylight comment is sitting in the earlier section before it breaks down into head types. So the way I read it, skylights of 32 sqft or less would be yes.
Other ceiling pocket exlusions are exclusive to uprights and pendents (standard and extended coverage). They appear to purposely be left out of the sidewall sections. BUT, what is interesting is that it does not have the same clarity on residential sidewalls. It appears as if by purpose (or oversight) that the ceiling pocket rules could apply to residential sidewalls.
Also, just a few other things to mention. Sidewalls are listed typically (if not always) for smooth ceilings. Per the definition of smooth ceilings, you could almost rule out ceiling pockets of all types for all sidewalls, but that could be a gray area. Also, remember that structural elements aren't necessarily defined as ceiling pockets if that is the scenario you have, BUT because of the smooth ceiling requirement, that shoots out the use of sidewalls under exposed structural construction (unless there is something I'm missing or sidewalls that are listed for his specifically).
Referencing NFPA 13 2019: In my opinion I would say no because code specifically provides the exception elimination of sprinklers within the pocket rules applies to standard spray and EC spray uprights & pendents as well as specific rules of residential sidewalls. No rules are indicated for standard spray sidewalls. Notice that residential sidewall ceiling pocket exceptions are different than upright and pendent pocket situations. Standard spray sidewalls depending on listing are 4"-12" down from the ceiling and have specific installation requirements below ceilings and soffits. Also depth of unprotected soffits are allowed to be up to 36" which would be unacceptable for sidewall use.
A key exception would be that looking at the definition of ceiling pocket per NFPA 13 2019 Handbook as it discusses certain minor depressions in ceilings can be protected by adjacent sprinklers (not specifying which kind). A example of a ceiling depressions is 8 in deep that isn't protected but is protected by sprinklers at the surrounding elevations that are 4 in below the ceiling at their locations. Such sprinklers are within 12in. of the high ceiling of the depression and as a result are in compliance with 10.2.6.1.1.1 and 18.104.22.168.1.1 requiring sprinklers to be within 1in.-12in from the higher ceiling.
Referencing the 13-19' Ed.
No they are specific to the type of sprinkler:
10.2.9 Standard Spray Uprights & Pendents
11.2.8 EC Uprights & Pendents - *notable that the section starts with including EC Sidewalls but is specific to Pendents/Uprights when allowing ceiling pockets.
12.1.12 Residential Sprinklers - *This section does not specify a specific sprinkler orientation, only "Sprinklers shall be..."
I think the caveat is the definitions of the ceiling types and how they play into the sprinkler uses:
22.214.171.124 - Flat - Continuous ceiling in a "single" plane.
126.96.36.199 - Smooth - "Continuous" ceiling free from significant irregularities (ceiling pockets)
3.3.25 - Ceiling Pocket "...bounded area of ceiling located at a higher elevation that the attached lower ceiling" which goes against the previous two definitions...
Just a guess (which could be part of a possible technical explanation): it is maybe related to the way sidewall sprinklers are activated in case of fire.
If the fire is below the sidewall sprinkler, the operation is similar as for an upright/pendent sprinkler.
If the fire is not located below the sprinkler, the heat plume and than ceiling jet to reach the sprinkler location is longer (then less effective/reliable) for sidewall than for other sprinklers.
It is one of the explanations for not allowing sidewall for extra hazard occupancy (in addition to the specific water distribution pattern).
And one explanation to have the ceiling as smooth as possible (more efficient ceiling jet toward the sprinkler location to activate it quickly).
If you have this in mind, you can understand when the ceiling pocket rule applies to sprinklers.
Depending on the configuration, you will have a chance to operate a nearby sprinkler (quick response) and you can omit protection in the ceiling pocket.
With sidewall sprinklers located on one side of the wall only, the ceiling pocket(s) will collect most of the heat and by the time you will activate your sidewall you may:
- either activate an unecessary large number along the wall
- or activate them very late, resuting in a possible uncontrolled fire condition for a large area.
I would personnaly not apply the ceiling pocket rule with sidewall sprinklers.
Skylight is slightly different because it is smaller in size and there are usually enough distance between 2 adjacent skylights.
Well said Franck. Had a hotel project that limited number of suites had beam ceiling features and GC did not understand why those rooms needed different protection than the single sidewall in most of the rooms. I said because we don't know where the fire will start and need smooth ceiling for the sidewall listings.. I
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