What Ceiling Height with Warehouse Ridge Vent?

11/4/2025

Good morning, I'm designing sprinklers for a Class III warehouse. The warehouse has a ridge vent that's currently enclosed on the side walls.

What ceiling height should be considered for the design: the average ceiling height or the height of the center of the ridge vent?

The lower part of the ridge vent is 39.66 ft, and the upper part is 41.5 ft.

If I consider 39.6 ft as the height, I could work with a 25.2 kPa sprinkler at 25 psi, but if I consider 41.5 ft, I should consider a pressure of 40 psi, and the fire pump would change.

Thanks in advance.

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9 Comments

Pete H

11/4/2025 06:58:40 am

For a gray area like this, I'd ask your AHJ directly as it is their call.

If you explain the cost impact, given the gray area, I'm pretty sure they'd let you go with the 39.6' height.

Jolber Torres

11/4/2025 09:27:32 am

Thanks my friend

Chris Nelson

11/4/2025 11:21:31 am

Is a false ceiling feasible? drops the ceilign height down

Dan Wilder link

11/4/2025 08:20:44 am

Ahh, a grey area open to interpretation.....

So the definition in 13 - 3.3.199 Roof Height - The distance between the floor and the underside of the roof deck within the storage area.

It does not mention vents or skylights, even though those have requirements for sprinkler protection if certain criteria are met.

Is the vent area big enough to warrant sprinkler protection within? That would be a good indicator on what the "effective" ceiling height would be for calculations and possible argument to use the lower ceiling height.

Franck

11/4/2025 08:25:52 am

As most if your sprinklers will be located higher than 40 ft, you will probably have to go to the higher demand. Even if you take the average between 39.6 and 41.5, you will end up above 40 ft.
That’s the downside of limits and changes. But more than 40 ft is definitely a challenge for any sprinkler protection, especially for warehouses (as an AHJ, I could be more flexible for a low hazard occupancy, but definitely not for storage where so many small deviations may occur and compromise the efficiency of you protection).

franck

11/4/2025 08:28:20 am

But it really depends on the number of sprinklers involved (if only a few, no problem, if many…)

jolber edilberto torres terrones

11/5/2025 10:40:57 am

Your comment makes a lot of sense, however it is still subject to interpretation by the AHJ, which in most cases is closed.

Jack G

11/4/2025 10:44:54 am

I also would ask the AHJ first but he will be coy I m sure if you aren’t absolutely sure of the answer.
I would use the logic of a sloped ceiling and go with the ridge vent being the highest area and design with the higher psi.

Anthony

11/5/2025 07:44:33 am

The "easy" option is to take the over 40 ft judgement and move on. I think this is best for your end user as well so they don't have to revisit this every time they get a new tenant or commodity. Assuming we're looking at 13-25, this also allows for an option to install a ceiling in the future for 30ft group A plastics.

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What Ceiling Height with Warehouse Ridge Vent?

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