Dormer Sprinkler Included in the Remote Area?

10/27/2021

I have a combustible attic framed with standard wood truss framing. There are dormers that are framed on top of the roof sheathing, that have small 2-ft x 2-ft openings in the sheathing to access the dormer and provide ventilation for the dormers. Both the attic and the dormers are fully protected by the dry system.

My hydraulic calculation area is 2,535 sqft, which is increased for slope and for it being dry.

A dormer falls within my remote area.

My understanding is that the dormer is considered a combustible concealed space per NFPA 13-2019. The small opening of 2-ft x 2-ft is allowed under NFPA 13 Section 3.3.195. Therefore, the dormer space should not be included in the hydraulic calculations, under NFPA 13-2019 Section 23.4.4.6.5.

I am being instructed by an engineer that this area is not qualifying as a concealed space and the additional sprinklers in the dormer need to be included in the hydraulic calculations. Adding the additional 8 sprinkler for the dormer to the already-calculated 34 sprinklers in the attic is causing the possibility of now needing a fire pump.

Am I wrong here?

Do the dormers need to be included in the remote area for this hydraulic calculation?

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7 Comments

Pete H

10/27/2021 06:55:14 am

By code compliance, I'd say you're right. You have excellent references that show the dormer to be a combustible concealed space and the access panel (provided there aren't a bunch of them in each dormer) doesn't seem to void it being considered that.

However, if the engineer of record on the job is claiming he wants to go beyond code and that he could see a fire in the attic causing the dormer sprinklers to go off at the same time as all the remote heads in the area, he is allowed to demand that, just make it so he understands that if your contract was only for code compliance, the extra costs of the fire pump will be on the client to provide as the calculation worked for code compliant based system.

JFP

10/27/2021 08:32:50 am

Completely agree with Pete H on this. If the EOR's concern is the small 2x2 opening then have the GC put in an access door or hatch. You could also run a calc for just the dormer to show that it works as a separate fire area. The other option is to include the 8 heads of the dormer but reduce the area of the main calc. If you're calculating two areas on top of each other then you should be able to count that floor area twice as part of the 2535.

Casey Milhorn

10/27/2021 08:34:56 am

Pete nailed it. You do NOT calc both levels of sprinklers in an instance like this. If you are a member of AFSA or NFSA, get an informal interpretation as well to back your statement up. I would definitely fight this one and submit for a change order. Money tends to get everyone's attention very quickly.

You could also ask the GC to remove all sheathing between the areas (if allowed by building code) and remove the lower level sprinklers all together. (if all else fails).

Jessica Lutz

10/27/2021 09:18:05 am

I agree fully with Pete and Casey...

I'd also include a ROM for a pump, including all the implications that go along with it (i.e. pump room requirements, emergency power if required by your code, testing, maintenance, etc.).

The owner trumps the EOR...have them make the final decision.

If the EOR wanted beyond the code, then they should've indicated as such at bid time.

Jack G

10/27/2021 10:35:29 am

Unfortunately, code officials, code compliance, sprinkler designers , are not the ones going to the fire to extinguish it.
Use common sense. If the opening is left open, include it , additionally in the design remote area. If the builder sheaths it off, don’t.
Better to be safe than sorry. When I estimated and performed preliminary layouts and bid calculations, you look at this….. you ask the question up front, so all bidders are on the same page and you all include the same coverage.
I would ask if it’s possible to unsheath, opening it up.
“ Ya mean your water pipe sizes are so tight , ya can’t afford 4 inch to the attic?”
Safety First !

Jesse

10/27/2021 11:22:31 am

I agree. I'd fight this one.

Alex

10/28/2021 08:09:44 am

I agree. I would say that the dormer does not need to be calculated. Is this a new system where you could simply upsize your distribution piping rather than adding a pump? I would push to have that CO on the engineer for requiring a system above the code and not properly covered or conveyed on Tier I drawings.

Dormer Sprinkler Included in the Remote Area?

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