Cost of Sprinklers in Wood Floor/Ceiling Cavities?

3/16/2022

We have a project that is Type III-A, wood frame construction, with an NFPA 13 sprinkler system.

The client is weighing options of filling floor truss cavities with non-combustible insulation versus adding sprinkler coverage within these floor-ceiling cavities.

Does anyone have recent experience to know the relative cost impact of adding sprinklers within these floor cavities?

Thanks in advance.

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8 Comments

Pete H

3/16/2022 07:28:53 am

No one is really going to be able to answer that without knowing the square footage of the structure.

Similarly, costs of labor vary heavily by shop (is it a union shop, is it a nonunion shop) and location.

Costs can also vary based on type of sprinkler and proximity to the sprinkler manufacturer.

Unfortunately the only way to really get an answer on this (that my inexperienced butt can think of) is put the project out for bid, and instruct bidders in your area to have the cost of protecting the floor/ceiling truss cavities as a separate line item as an alternate. Then instruct structural bidders (or whatever trade would handle the insulation in your area, not my field) to do the same with the insulation costs. Make sure the insulation you're asking for is detailed for the right type and capacity to make it so you can omit sprinkler protection in the interstitial space.

Compare the separate line items. Come up with works best for your project.

Jesse

3/16/2022 08:09:40 am

Its really difficult to answer that. The combustible concealed space is a volume of space. If these cavities between the ceiling and floor are 1-ft high, the cost of insulation will be substantially less than if they are 4-ft.

The cost of automatic sprinkler protection would largely be consistent.

Anthony

3/16/2022 08:56:50 am

Generally its fairly easy to get a price for insulation. So start there and work that against a sq ft number for the rest of your building's sprinkler cost that should be a decent ballpark number.

I think its always a better idea to go the insulation rout. You improve the heat zoning in a building and insulation doesn't need to be serviced and does leak.

If pipe is already going to be in the truss cavity and the truss is 36+ inches deep then Its worth thinking sprinklers in the cavity due to the large volume of insulation required.

As others have stated there is no "rule of thumb" as each instance requires a V/E analysis for the particular geometry and local cost factors.

Alex

3/16/2022 11:11:13 am

I agree with Anthony here. You also need to be careful when your cavity size gets large. The code outlines limits on amount of insulation that can be installed.

Wendell

3/16/2022 11:07:38 am

Coming at this from the architectural side, contractors we've worked with have always preferred the "fill voids with insulation" solution, but that's for voids that are generally no deeper than 24" or so. Note that some floor/ceiling or roof/ceiling assemblies have limits on amount and type of insulation that can be added, and/or require an additional layer of gyp if fiberglass insulation is used, so check Gypsum Association or UL assembly notes before proceeding.

sean

3/16/2022 07:52:33 pm

I think you also have to consider that if you are already running branch lines the additional heads are a cost but significantly less than a new system

Rock

3/17/2022 09:34:12 am

Be sure to loop in your AHJ. The AHJ may require a third party inspection of the insulation in the interstitial space due to the difficulty of completely filling the cavity from the underside.

Note: NFPA 13 will only allow a small gap at the top of the insulation after the insulation settles.

Thomas A VonCannon link

3/17/2022 04:21:38 pm

Insulation filling a void, locally when this is done it is blown in above chicken wire to maintain a filled void. I would think that when the void is over 24" deep, I would think sprinkler protection would start to be competitive with insulation. In most cases where this takes place you have a branch line within the cavity anyway, so you are talking the cost of a weld-o-let a sprig and sprinkler head.

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Cost of Sprinklers in Wood Floor/Ceiling Cavities?

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