An Easy Process for Sprinklered Middle Housing?

6/2/2025

We are on the AHJ side, and Middle Housing requirements are on their way to increase density and reduce the cost of housing in our area. This will allow existing single-family residences to subdivide their lots, which may have up to four additional dwelling units on a parcel.

In anticipation of this, we are exploring options for residential fire sprinkler requirements beyond our already existing code for these small, ADU (Accessory Dwelling Unit) type structures of 1,000 sqft maximum.

We would like to maximize the possibilities of this by making the process as easy and inexpensive as possible.

One avenue we are interested in is allowing for P2904 flow through sprinkler systems (Section P2904 of the IRC, prescriptive standard for one- and two-family dwellings) that can be installed by a plumber. We are open to omitting the fire plan review process and possibly even a bucket test, but still inspect for head placement, tenting, etc.

What are your thoughts?

Has anyone looked at this with any degree of success?

We would love to hear any feedback you could provide.

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6 Comments

Dan Wilder

6/2/2025 08:07:31 am

While I would push for some oversight for calcs and final acceptance (water flow), NFPA published a good article about "Tiny Homes" that could be applied to the ADU's.

With the multipurpose systems, enforcement (a checklist) of 10.4.2.3 and use of the prescriptive sizing methods as outlined in 10.4.9 would be priority for me. These can be done with some basic worksheets and MFG details and should not take a lot of time for review.

https://www.nwccog.org/wp-content/uploads/2022/07/WhitePaperTinyHomes.pdf#:~:text=This%20white%20paper%20contains%20some%20basic%20information%20about,these%20documents%20as%20of%20the%20date%20of%20publication.

Ricardo Gonzales Jr

6/2/2025 08:20:18 am

I would require a plan for preliminary approval. It can be pushed to a 'walk through' type permit to make it simple and inexpensive. The plumbers in Colorado who residential like this description have taken a 4 or 8-hour class to understand what they are expected to do for this system. It's not difficult but identifies design options and routings of the piping.
The biggest complaint will be running all the piping to the sprinklers, but I feel they will quickly disappear once they've installed a few.

Anthony

6/2/2025 09:01:09 am

I like where the heart is in the P2904 section of IRC. The code is trying to make residential sprinklers "easier". More sprinklers are better than less and the P2904.6.2.2 calc's can be handled by someone after a 4hr class and some mild mentoring.

I think my biggest worry will be inspection and certification of these instillations. I can see a world where the same calc is used over and over as "boiler plate paperwork" and no one catches it. So like everything its in the enforcement and review of this work. An additional fee on the permit ~200$ should cover an inspectors time.

I could see this as being a great extra revenue source for volly firefighters in their off time, good community outreach too. I can see a lot of good with a program like this. Could probably "certify" some local commercial sprinkler inspectors/inspection companies to do this work too if a 3rd party was required.

I think the success will go largely unnoticed like with all sprinkler successes, a small fire is suppressed and never becomes a large fire. Hard to document that kind of negative success

Jesse

6/2/2025 09:29:14 am

I'm not sure I'd get behind the lack of a plan approval process. Without a doubt, I think the layout and hydraulic calcs should be looked at by a qualified plan reviewer. I can see circumstances where the same calcs are just used over and over and over.

Jay

6/4/2025 07:52:55 am

What is a bucket test?

Jeff

6/8/2025 06:59:33 am

I don’t see how taking a 4-8 hour class makes a tradesman a licensed qualified sprinkler fitter. Someone will be held responsible when the insurance company refuses to pay for damages when it is discovered that a defect in installation has caused water damage and personal injury. Public safety is the name of the game. Save a buck lose a life.

An Easy Process for Sprinklered Middle Housing?

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