Sprinkler Concealed Space if Minimal Wood?

11/29/2022

I'm working on a mid-rise 5-story residential building.

The building structure is permitted to be combustible construction per 3.2.2.50 of the National Building Code of Canada.

For sound proofing the developer decided to build with cast in-place concrete columns and slabs, but decided to use combustible studs for the interior partitions .

So far, nothing wrong here. Now being that the ceiling is 10-ft high, a drop ceiling was built creating a concealed space for the duct and wiring and so on. The architect says that the top part of the interior combustible partition needed not to be drywalled inside the concealed space to the underside of the concrete slab.

The concealed space is made up of a concrete slab with fire separations sealed to the underside of the slab containing every unit individually without sharing any concealed space with the other units.

On the other hand the sprinkler guy says that the exposed 2x4 studs surface in the concealed scape are not considered "limited combustible material," per NFPA 13 Section 8.15.1, and the space should be sprinklered or filled with non-combustible insulation.

Being that the building was permitted to be of combustible construction and the developer went above and beyond with the concrete structure, I'm not sure whether the space needs to be sprinkler protected or not.

Anybody had this scenario happen before, and if so, how should it be addressed?

Thanks.

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11 Comments

Paul Pinigis link

11/29/2022 08:09:00 am

What is the construction of the suspended ceiling? Does it include wood that is exposed in the concealed space? If so, how much?

James Johnathon Phifer

11/29/2022 08:12:01 am

If the wood joists are exposed above the ceiling, then the space is considered combustible and must be protected.

Glenn Berger

11/29/2022 08:12:51 am

Probably need more information. How much exposed wood is located in the proposed unsprinklered space? It would be easy to eliminate any questions and just conceal the wood within the drywall.

Patrick Drumm

11/29/2022 08:25:52 am

I agree with Glenn. Also, depending on the number of walls, this may be the most cost-effective options as well. If I were the owner, I would request change order proposals for both options to compare.

Connor

11/29/2022 08:19:09 am

Per NFPA-13-2016 8.15.1.1, sprinkler protection is required where you have exposed combustible construction. The partitions are constructed with combustible materials, and those materials are exposed in the concealed space above the ceiling. Therefore, it requires sprinkler protection. If they are separated with adequate construction, you may be able to omit sprinkler above some small isolated compartments not exceeding 55 sq ft such as bathrooms.

Options include:
1. Sprinkler the space above ceiling.
2. Fill the space with noncombustible insulation.
3. Sheetrock the walls all the way up to the concrete deck above.
4. With AHJ approval, apply intumescent coatings or other fireproofing to the exposed wood construction.

Depending on where you are in the construction process, some options may be cheaper than others.

Alex

11/29/2022 08:47:42 am

I would simply encase the portion of the wood columns above the ceiling within drywall. You cannot have combustibles above the drop ceiling.

Jesse

11/29/2022 09:33:06 am

The combustible material above the drop ceiling is the issue. Still don't know a lot of data here, but seems like your sprinkler guy is right.

Franck

11/29/2022 10:46:40 am

Be careful, there is a difference between what the construction code allows and what is necessary to be protected.
You can have a combustible building (made with sandwich metal panels and combustible insulation, for example), that complies with the construction code, but that does not mean that you don't need to protect it... against its construction elements.

As indicated above, it all depends on the quantity of wood in your case and if you consider it as combustible, or limited combustible.
If considered combustible by your sprinkler guy, then sprinklers are required !
Better trust the fire protection guy than the architect ;)

Clement

11/29/2022 11:28:50 am

Description,

The conceal space is made up of a 10`` concrete slab and the suspended ceiling is framed with metal channel and finish with 1/2`` gypsum. The fire separation is drywall to the underside of the slab and the only exposed wood is from the top of the interior partition, basically about 8`` of the face of a 2x4 wood stud,

Corey Eppinghaus

11/29/2022 12:10:35 pm

Are you sure about the 3.2.2.50 because I'm looking at the 2020 NBC and 3.2.2.50 is 3 storey non combustible

11/29/2022 12:23:31 pm

Corey,

Sadly in the Province of New-Brunswick we are still under the 2015NBC

Sprinkler Concealed Space if Minimal Wood?

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