What to do? Solutions to prevent pipe freezing violate code

Marc Millis
August 12, 2019

DILEMMA: I have pipes that freeze (when < 10 deg F, few days/yr), but both possible fixes violate code. Option A: heater cables require accessible pipes, but the pipes need heat where the are either too close to wood or in a wall. Option B, is to convert the gap between the floor joints (where the pipes run) into the heat supply duct for the kitchen.

SITUATION: 1950’s era house, An exterior kitchen wall extends beyond the foundation wall by about 20” out , and 22” above ground The water pipes run along that extended floor and up the external wall.

MORE ON OPTION A: Plumbing Heat Cables are only supposed to be attached to plumbing that is in the open. The pipes need heat where they are too close to the exterior floor and up into the wall, where such heat cables are not supposed to be used. There is about 5’ of pipe upstream of that which is accessible (but with bends and valves). I’m not sure if putting heat cables on those accessible parts will keep the other sections of pipe warm enough.

If I did attempt to attach the cable to the pipes above the extended floor (before they go up into the wall), I’d have to reach 24“ laterally into the cavity between the floor joists to secure the cable to the pipes. I can only get my hands in there about 9” considering all the obstructions.

MORE ON OPTION B: I considered re-routing the heating duct for the kitchen (which is close by) so that it runs through the cavity between the floor joints and then up through the interior floor to the kitchen cabinet - putting the register at the toe kick of the cabinet. The problem here is that converting the cavity between floor joists into a HVAC supply duct violates code. It’s also a code violation to have plumbing inside ducts.

I’m not sure which wrong solution is less wrong or risky.

Comments (13)

  • deb s

    Is it the kitchen pipes that freeze or second floor above kitchen as well? I get frozen pipes in my basement bathroom and have found a space heater and running the fan/vent eliminates the problem - pushes warm air into the subfloor area just enough as my plumbing comes in from the ceiling. -- so if you can get heating in the basement above the kitchen on that wall - maybe close up the 20" overhang and insulate well

  • branson4020

    Assuming both hot and cold water lines in that wall, maybe a hot water recirculating system would help.

  • apple_pie_order

    Look outside the box: where can you move the pipes so that they will be warm enough?

  • yvonnecmartin

    Some people just let the faucet drip when it is predicted to get that cold.

    Another trick is to leave the cabinet door open so that the inside heat gets to the pipes.

  • erinsean

    Can you put insulation between pipes and outside wall? We keep our vanity door open on very cold nights..

  • PRO
    GN Builders L.L.C

    Insulate the pipes and the cavity over the pipe, whats the problem? Done all the time.

  • PRO

    You need an HVAC/local guy. On site. Failing that, for the few 10 degree days, open all the cabinets and make certain the house itself is warm enough.....and leave a tiny drip running.: ).

  • Jake The Wonderdog


    I live where it gets -15 at times. The first thing is to avoid running pipes on outside walls altogether if possible. Moving the pipes out of the wall so they come out of the floor of the base cabinet is common.

    Assuming you have moved them as best you can already, the other answer is to put insulation between the outside wall and the pipe and leave the area between the pipe and the warm interior un-insulated. See crude diagram

    Use RMax (highest R value per inch) and layer it if you need to between the outside wall and the pipe. Also insulate the walls of the studs.

    Alternately - you can use spray foam to make the same insulated channel for the pipes, but you need to remove the pipes first to do a decent job. Using spray foam has the advantage of sealing any air leaks.

  • Marc Millis

    Thank you all for your comments. Some clarification: Though I realize the ideal solution is to relocate the pipes (would require remodeling the whole kitchen) - that scale of effort is beyond my resources. I'm looking for the safest way to redirect heat to the portions of the pipe that I can already get to, without ripping apart walls. I've already added insulation where I could get at it. I already leave the cabinet doors open on those coldest days - and it still froze.

  • greg_2015

    Where do the pipes go? Is it just the supplies for the kitchen or are they travelling up to the second floor?

    What about creating an opening in the back of the cabinets so that the pipes are exposed there? Then the heat from the house can get into that cavity better.

  • Marc Millis

    The pipes only go to the kitchen sink. I am indeed considering opening the back of the cabinets to expose the pipes, in addition to adding heat cables to the exposed pipes, and converting the channel between the floor joists into a heating duct. I've not probed inside the wall to determine the fidelity of insulation. Where the floor juts out beyond the foundation block wall, there was only wood. I added what insulation I could wedge in between that wood and pipes.

    I've made a crude (not to scale) sketch.

  • greg_2015

    If that's the case, then just repipe that section with pex that goes down through the bottom of the cabinet.

    Marc Millis thanked greg_2015
  • Jake The Wonderdog

    What Greg shows is exactly what I was saying about routing through the bottom of the sink base instead of the wall. Doing that in PEX will be easy to route and if PEX freezes it will be less likely to crack.

    That cantilever can be spray foamed as well. There are small spray foam kits sold online.

    I'm not endorsing the company or product - just saying that it's there.

Need help with an existing Houzz order? Call 1-800-368-4268