GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Fire-Protected Floor Over Crawlspace

lukasmpeter | Posted in Building Code Questions on

Change is hard!
I designed a ducted mini-split system for a new 1,800sf all electric home in the Southern California desert. The permit plan reviewer is requiring the floor to be fire protected per CRC R 302.13.  because the ducted mini-split air handler and ductwork is located in the sealed non-vented crawlspace.
Floor fire protection requires either 1/2″ gypsum wall board or 5/8″ wood structural panel membrane applied to the underside of the floor framing members. The code makes this requirement for floor assemblies located directly over a crawlspace for the installation of “fuel-fired or electric-powered heating appliances”.
I believe mini-split air handlers don’t fall into that category but can’t find the supporting code language. No backup resistance heat coils are specified.

The loads are: sens. 17,871, lat. 897, tot. 18,769, shr 0.94, outside design temp  is 109F.
I prefer to use Fujitsu’s vertically mountable ARU18RLF in a wall closet but wasn’t able to bring the cooling loads into it’s operating range.
I ended up specifying Mitsubishi’s PEAD-A24 that has to be mounted horizontally.
Locating the air handler in the crawlspace it not my first choice but the house has no attic or dropped ceilings.

Has anybody run into this code issue or am I missing something?

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. walta100 | | #1

    It may be a better investment to build a full basement that would not need the fire protection layer and would add resale value.


    1. Expert Member
      MALCOLM TAYLOR | | #2


      If he included a crawlspace as a service cavity to locate the ducts and equipment, how would it help to have a full basement?

  2. walta100 | | #3

    If he built a full unfinished basement instead of a crawlspace he would not be require a service cavity and no floor fire protection would be required. He would need a staircase and smoke alarms.


    1. lukasmpeter | | #4

      Thanks Walter and Malcolm. I am considering to build what is locally called a California basement, a partial basement just for equipment access and a few bottles of wine but I would prefer to spend the budget on efficiency measures.
      To the original question: are mini-split air handlers equivalent to fuel burning or electric resistance heating appliances? I am having a hard time understanding how they pose a similar fire risk.

      1. Expert Member
        MALCOLM TAYLOR | | #5


        What are you using to frame the floor above? There is an exception for both dimensional lumber which is 2"x10" or deeper, and I-joists if they have a fire treatment.

        "Wood floor assemblies using dimension lumber or structural composite lumber equal to or greater than 2-inch by 10-inch (50.8 mm by 254 mm) nominal dimension, or other approved floor assemblies demonstrating equivalent fire performance."

        Fair or not, on plain reading of the provision I think you face an uphill battle trying to convince them a heat pump isn't an "electric powered heating appliance".

  3. walta100 | | #6

    In general auguring with code enforcement is a lot like yelling at the clouds. You might feel better but you are not going to change any opinions.

    All too often enforcement sees themselves as gods with the power to spend your money. Even when they are flat out wrong the person that made a call tends to stand by the wrong call for as long as humanly possible grasping at every straw for fear that should you get them to take one step back then every call they ever made is now in question.

    You can politely ask if an air handler supplied by one 20 amp circuit is considered a heating appliance. But understand you are treading on thin ice once he understands this is heat pump only without backup resistance you could be opening another can of worms where he wants to require the resistance back up heat.


    1. capecodhaus | | #11

      Well said. Sage advice. Give this guy an EXPERT MEMBER status..

      Gba seems to hand them out like candy

  4. lukasmpeter | | #7

    Thanks for the code pointer Malcolm, this is probably the least costly structural change I could make at this point. Floor framing is designed as 2x6. Maybe I can skip a row of girders and go to 2x10 framing, brilliant!
    Thanks Walter, back-up heat request is a real worry. I agree, challenging code officials without an applicable code section is not a good use of time.

    1. Expert Member
      MALCOLM TAYLOR | | #9


      I'd go with deeper joist spanning farther anyway. From an engineering perspective remember that:
      - Doubling the depth of a joist allows it to carry four times the load.
      - If you double the depth of a joist it will deflect 1/8 of the original amount.

  5. PBP1 | | #8

    R302.13 Fire Protection of Floors: "Floor assemblies located directly over a crawl space not intended for storage or for the installation of fuel-fired or electric-powered heating appliances."

    I like Walter's "You can politely ask if an air handler supplied by one 20 amp circuit is considered a heating appliance."

    Is the air handler merely a fluid heat exchanger? Unless there's some sort of electric resistance heating emergency backup going on with that air handler, I think there's an argument that it is not an "electric-powered heating appliance", that's the air source heat pump outside.

    People have electric exhaust fans in crawlspaces, even with ducts, an air mover is an air mover. The fact that there's somewhat hot fluid, maybe if you let them know how hot that fluid gets (don't know but maybe less than 200 F?) that might help.

    Is there any code/code experience for hot water pumps for water heated floors versus where the source of heat energy is located? Seems like a viable analogy, or even geothermal heat pumps and indoor movers.

    From a presentation:
    This modification maintains the provision for appliances and includes electric-powered appliances in addition to fuel-fired ones. Because there are many other types of appliances, such as sump pumps, that are less hazardous than heating appliances, the restriction is now limited to heating appliances.

  6. lukasmpeter | | #10

    Thank you very much for the excellent advice PBP1 and Malcolm!
    The crawlspace is encapsulated, it makes a lot of sense to increase joist spans in order to reduce girder lines and subsequently pier footings. Right now I am looking at an army of pier footings and envision someone taping the crawlspace vapor barrier on all those penetrations.
    I do have to do some educating on the proposed heat-pump system, another plan check note states: "show source of combustion air to fuel burning appliances: AH1 in unvented crawl space" (the lack of an exhaust was not noted though). The language from the ICC presentation will definitely be helpful.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |