Sprinklers for Concealed, Raised Wood Platform?

10/28/2025

We have a church with a raised platform (wood construction) that is not accessible and is a concealed space. We typically have not provided sprinklers for this type of space. The AHJ is stating sprinklers are required per NFPA 13.

Are sprinklers required for a combustible, concealed space below a raised platform?

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7 Comments

Pete H

10/28/2025 07:25:03 am

Check NFPA 13 to whatever your AHJ's current accepted edition is.

I'm still in 2016, so for me it would be

8.15.6: Spaces under ground floors, exterior docks, and platforms.
8.15.6.1 Unless the requirements of 8.15.6.2 are met, sprinklers shall be installed in spaces under all combustible ground floors and combustible exterior docks and platforms.
8.15.6.2 Sprinklers shall be permitted to be omitted from spaces under ground floors, exterior docks, and platforms where all of the following conditions exist:
1) The Space is not accessible for storage purposes and is protected against accumulation of wind-borne debris.
2) The space contains no equipment such as conveyors or fuel fired heating units
3) The floor over the space is of tight construction.
4) No combustible or flammable liquids or materials that under fire conditions would convert into combustible or flammable liquids are processed, handled, or stored on the floor above the space.

----

I'd look for an equivalent section in your current code, but see if the omission applies to your space.

Donnie

10/28/2025 07:59:15 pm

Clearly all 4 conditions exist that would allow you to omit sprinkler protection from the concealed space underneath the platform.

Chad

10/28/2025 08:11:51 am

Just fill it with non-combustible insulation? That would be a better alternative for an existing condition than sprinklering a blind space under a stage that will never get inspected, ever. IMO.

Don't bother with chopping it up to 160 cu ft spaces, just fill it. Would be better for sound if they are using the stage as a stage as well.

Anthony

10/29/2025 08:22:10 am

I was thinking about this a bit yesterday. what if there is a floor/basement beneath the platform doe this then qualify as a ceiling combustible space?

Wes

10/29/2025 08:39:36 am

I was curious to begin with (but hadn't weighed in yet) why it wouldn't qualify as a combustible concealed space to begin with, even without a floor below?

Is the hazard of a combustible concealed space not the same to that room regardless of whether there's a basement below or not?

Anthony

10/31/2025 08:01:53 am

@wes

Well I can hear an argument if this is a wood structure with protection above from a sprinkler system you don't have a full 3D fire. The fire can only grow vertically similar to a pallet fire. (I'm not saying we need K25s for a church alter). Thus the sprinklers over head would suppress the fire long enough to allow evacuation and not cause other floors specifically floors below the structure to be enveloped. Specifically if this was a platform built on a concrete slab on grade. In that instance there are significant differences to a horizonal flue space created by a ceiling cavity, or at least that's what I would argue.

Jack G

10/29/2025 04:39:50 pm

I m assuming that you are talking about a raised combustible wood “ altar “ that is walked upon by church priests/ ministers.

One would also have to question if electrical ( outlets/wiring ) are run in the concealed combustible space, ductwork, speakers, large receptacle boxes. Also these alters can be dressed with apoulstry( combustible cloth ) too.
Height of the altar platform ( 6 inches or less ) although I m imagining this as , stepped — to 3 feet high so the ministers heads are above the church goers.
AHJ s in my 3 states require them un less they are 6 inches or less. Or built compartmented like my above response. Half a century ago, as an altar boy I remember tripping over the pipe in/ out lol. Go figure.

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Sprinklers for Concealed, Raised Wood Platform?

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