Dry-Pipe Water Curtain for Open Parking Garage?

1/19/2023

I am working on a 4-story multifamily building that's above a 1-level parking garage on the ground floor.

The exterior wall is less than 10-ft fire separation distance to the property line, requiring the exterior wall it to be 1-hour fire-resistance-rated.

Since it is an open parking garage, I need a lot of openings within this wall to provide ventilation. Denver has an amendment that allows 50% allowable openings with water curtains per NFPA 13.

Since the parking garage will have a dry system, is this even possible?

It seems like a very odd condition but again I need over 25% opening within the wall to comply as an open parking garage.

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6 Comments

Anthony

1/19/2023 07:25:08 am

Assuming you're describing a water curtain as outlined buy NFPA 13-16 8.15.4.1, 15.17.2 and 11.3.3 yes you can use a dry system.

I would however look at a dry(pneumatic) pilot deluge system dedicated to your water curtain(s). otherwise, you'll have to add the curtain to your calc and the pipe sizes will get huge.

Big caveat here: This is not a proscriptive design method in NFPA 13 so you're out on a limb here a bit. I mean to say this sounds like a rule made up by a building official not an FPE. You may want to consult NFPA 80A and 15 as well as FM 1-20.

Todd E Wyatt

1/19/2023 08:32:35 am

Here is the prescribed requirements for the referenced “Water Curtain’s” per an amendment to 2021 IBC 903.2.11.1.4 :

2022 DENVER BUILDING CODE & DENVER FIRE CODE
Section 903.2.11.1.4 Exterior wall openings is added as follows:
903.2.11.1.4 Exterior wall openings.
Where exterior wall openings are permitted by Table 705.8 of the Denver Commercial Building Code to be up to 50 percent of the exterior wall area openings shall be protected by closely spaced sprinklers, 6 feet on center and located within 6 to12 inches of the wall. The sprinklers shall distribute a minimum of 3 gpm per linear foot of wall opening. The building shall be protected by an automatic sprinkler system complying with the Section 903.3.1.1 or 903.3.1.2. The sprinkler system hydraulic design shall comply with the “Water Curtain” design method in accordance with NFPA 13.

The referenced Table 705.8 limits the maximum allowable area (MAA) of exterior wall openings (EWO) based on Fire Separation Distance (FSD). A FSD of >5-feet & <10-feet permits a 25% MAA of EWO. The Denver amendment (903.2.11.1.4) permits this to be increased to 50% if a “Water Curtain” is installed.

An “open parking garage” requires “two or more sides” to have “uniformly distributed openings” including an aggregate length of openings of not less than 40% of the tier perimeter and an aggregate area of openings of not less than 20% of the tier total perimeter area :

2012 IBC
406.5 Open Parking Garages
Open parking garages shall comply with Sections 406.2, 406.4 and 406.5.
406.5.1 Construction
406.5.2 Openings
For natural ventilation purposes, the exterior side of the structure shall have uniformly distributed openings on two or more sides. The area of such openings in exterior walls on a tier shall be not less than 20 percent of the total perimeter wall area of each tier. The aggregate length of the openings considered to be providing natural ventilation shall be not less than 40 percent of the perimeter of the tier. Interior walls shall be not less than 20 percent open with uniformly distributed openings.
Exception: Openings are not required to be distributed over 40 percent of the building perimeter where the required openings are uniformly distributed over two opposing sides of the building.
Open Parking Garage
406.5.2.1 Openings Below Grade
Where openings below grade provide required natural ventilation, the outside horizontal clear space shall be one and one-half times the depth of the opening. The width of the horizontal clear space shall be maintained from grade down to the bottom of the lowest required opening.

David T Williams

1/19/2023 09:47:02 am

Often the reason an "open" parking structure is provided is to avoid the costs of fire protection sprinklers and ventilation.... since you already have sprinklers in the structure it would seem that the cost of a ventilation system could be significantly lower than the water curtain you are talking about.

Brian Cockburn

1/19/2023 10:06:09 am

I've done water curtains on dry systems as you describe quite a few times. They are certainly possible. Every time I've done this there has been a code consultant who prescribed the performance requirements (flow, pressure, k-factor, etc.) so I didn't have to come up with them. I recommend you find a consultant to help you with that as well.

Franck

1/19/2023 10:09:54 am

I an always confused with the use of water curtains as an alternative to rated fire walls. From an insurance loss prevention perspective, if you need a rated fire wall, it has to be a passive protection, i.e.: independent from your automatic system, including the water supply.
Why? Because if tou have an appropriately designed sprinkler system, you don’t need a rated fire wall, unless your automatic protection is impaired. So having a sprinkler protection for active protection AND water curtain for the “passive” protection does not answer the possible issue of losing the water supply (common impairment for both systems).

Then, if your parking is not sprinkler protected, which could be allowed for open structures, you may have a total loss in your building.
There has been a series of recent events with total loss and hundreds of damaged vehicles in open parking structures.
One interesting loss is the one that happened in Liverpool (UK) on New Year’s night of dec 31 2017. Just google “liverpool car park fire” for more information.

Glenn Berger

1/19/2023 05:26:09 pm

Yes, providing a water curtain in a dry system is definitely permissible.

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Dry-Pipe Water Curtain for Open Parking Garage?

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