Fire Sprinklers and Overhead Doors: A Love Story

I've heard that in order to publish on the internet all blog post titles must have a gripping click-bait title. This was my best attempt. Sorry to disappoint, but there is no love story here.

Things are back on track this week - the last got a little busy at home last week when my wife and I welcomed our third child to the family. Even with the third, it's amazing how much joy and motivation kids can bring with their arrival. 

Needless to say I didn't have a whole lot of productivity last week, but I'm very glad you've tuned in. This week we're exploring requirements and challenges of sprinkler protection near overhead doors. 

Where Required

​Sprinklers are required under "fixed obstructions over 4 ft (1.2 m) in width." (NFPA 13 - 2002-16 8.5.5.3.1, 2019 9.5.5.3.1)

One common application for this code section is overhead doors in the "open" position. Annex material even specifically references overhead doors as an applied example of this requirement.

Sprinklers are required where the horizontal projection of an overhead door exceeds 4-feet.

Application of the 4-ft Obstruction Rule

If the overhead door doesn't create an obstruction over 4 feet (1.2 m) in width, then a sprinkler is not required to be provided beneath the door. This dimension is typically applied in the horizontal dimension only, and is measured as the horizontal projection of the edge of the door away from the wall.

Depending on how creative things want to be architecturally, sprinklers can be avoided beneath overhead doors when the door assembly doesn't create a 4-foot horizontal obstruction. This can be the case with small coiling doors, door tracks that only run vertically up a wall, or a combination of vertical and horizontal tracks that don't project more than 4 feet out away from the wall.

Hanger & Supporting Challenges

​NFPA 13 does not specifically address support for sidewall or upright sprinklers below an obstruction, but similar requirements can be extracted from criteria on pendent sprinklers served by branch pipe above a ceiling.

If a sprinkler's horizontal steel branch pipe feed is greater than 1'-0" for systems with 100 psi or more, or greater than 2'-0" for any steel system, then a hanger is required to support the armover (NFPA 13 2002-16 9.2.3.4, 2019 17.4.3.4).

This presents a natural challenge as the door track is typically only designed to support the forces of the door and is not considered to be building structure capable of supporting the sprinklers, pipe and fittings. While it's very common for installers to attach the hanger to the door track, many see this as a violation of the hanging rules of NFPA 13.

Supporting sprinklers beneath the overhead door can be a challenge due to the height differences between the door and the ceiling/roof structure above.

Drainage & Dry Systems

Protection beneath overhead doors ramps up to another level of difficulty when used in dry systems. If a sprinkler beneath an overhead door on a dry system traps water, there needs to be a means to drain the trapped water and for dry systems in an unheated area, would require an auxiliary drain and drum drip.

While this might not present a challenge with a single overhead door, multi-bay vehicle buildings could wind up having a low-point drum-drip for every or nearly every other overhead door.

Aside from the cost, these drum drips are a maintenance nuisance as failure to drain these on a regular basis could result in a freeze and rupture of the drain assembly.

New Guidance on Sprinkler Position & Types Below Obstructions

Fortunately - in an update that I find very helpful - the latest edition of NFPA 13 now addresses where sprinklers can be located beneath obstructions.

Sprinklers are required to be either located beneath the obstruction, or with their deflector no more than 3 inches off the side of the obstruction (see below). This was clarified in 2019 based on fire testing & research.

New guidance for sprinkler protection beneath obstructions - new to the 2019 edition of NFPA 13.

Where a sprinkler is adjacent to the obstruction and not directly beneath, it must be an "intermediate-level rack type" (NFPA 13 2019 9.5.5.3.1.3). These sprinklers are provided with a shield that prevents inadvertent cooling from sprinkler discharge above (the shield is ineffective and not intended to help "collect" heat).

Your Challenges?

What tips & tricks have you come across when dealing with sprinkler design around overhead doors? This site is created to start the discussion. Add your questions, tips & tricks in the section for your comments here.

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