I forgot to install the floor sensor. Now what?

Will underfloor heating work without a floor sensor?

Yes, but between electrical code compliance and achieving a more efficient system, you’ll want to use one. Sometimes even the most organized installer forgets an important detail. If you forgot to install the sensor (typically placed between runs of heating wire and encased in thinset to control your floor temperature) and already finished the flooring, don’t panic! Try these tricks to control your floor temperature.

Option 1: Set the thermostat to use ambient air mode.

Set the thermostat to ambient air mode, if it is available on your thermostat model. This will sense the temperature around the thermostat and adjust the floor heat accordingly. Please note that this may cause some issues in reaching your desired temperature. If the area is warmer or gets direct sunlight, it may not kick on the floor heat. Also, if there is an air conditioner blowing cold air directly into that room, the floor heating system will continue to heat.

Option 2: Chisel out some of the grout between the tiles.

1. If your drywall is already in and your grout lines are at least 1/4” wide, you may run your sensor wire from the control location behind the wall and fish it out through a hole near the floor by using a fish tape or a nail on a string.
2. Use a cutting tool and gently remove the grout from between the tiles for a distance of 6–9 inches into the heated floor. Be careful not to cut too deep and damage a heating wire. Locate the sensor between the tiles, but make sure not to put it directly on top of a heating wire.
3. Re-apply grout and then cover the sensor hole in the wall with trim.

Option 3: Install the sensor under the subfloor by accessing the joist bay.

If your grout lines are not wide enough, or if you are uncomfortable with cutting the grout AND you have a raised foundation (not concrete), you may be able to fish the sensor wire below the subfloor.

1. Use a 1/4” drill bit to carefully drill a pocket under the heated floor in the subfloor up to the underlayment. (Stop before you get to the mat!)
2. Secure the sensor in the pocket with adhesive and then insulate.