What is this?
Electric underfloor heating uses either heating cables or mat systems embedded in or under the floor to provide warmth. When it stops working, the floor remains cold. These systems are common in bathrooms, kitchens, and conservatories in UK homes. Faults can be in the heating element, the thermostat, or the electrical supply.
Common causes
- Faulty thermostat or floor sensor
- Damaged heating cable — often caused by drilling or nailing into the floor
- Tripped MCB or RCD on the underfloor heating circuit
- Faulty relay or contactor in the thermostat
- Loose wiring connection at the thermostat or junction box
- Failed heating cable due to age or manufacturing defect
Is it dangerous?
Electric underfloor heating that is not working is not dangerous. However, if the circuit trips when you turn it on, there may be a damaged cable creating an earth fault. Do not keep resetting the circuit — call an electrician.
Can I fix it myself?
Check the thermostat settings and make sure it is calling for heat. Check the consumer unit for a tripped MCB. Some thermostats have a built-in diagnostics screen that shows error codes — check the manual. If the thermostat display is blank, check the fuse in the spur feeding it.
When to call an electrician
Call an electrician if the thermostat seems fine but the floor is cold, if the circuit trips when the heating turns on, if the thermostat shows an error code for the floor sensor, or if the heating stopped working after any building or flooring work.
What will an electrician do?
Test the thermostat and floor temperature sensor
Measure the resistance of the heating cable to check for breaks or damage
Inspect wiring connections at the thermostat and junction box
Use thermal imaging to identify cold spots indicating cable damage
Locate and repair cable breaks if accessible
Replace the thermostat or floor sensor if faulty
Typical cost
£100 – £350
Thermostat and sensor replacements are at the lower end. Locating and repairing a damaged cable under tiles can be significantly more expensive due to floor access.
