The Do’s and Don’ts of Underfloor Heating

If you have never installed underfloor heating before it can seem complicated and very technical or maybe you have installed a couple of jobs but are not confident in the procedure yet. This basic guide of Do’s and Don’ts is designed to help you avoid some of the pitfalls encountered when installing electric underfloor heating.


  • Read all the instruction guides in full before commencing installation – these are designed to help you get the install right the first time and not just for looking at if you run into trouble.
  • Remove the protective film before installing Thermonet underfloor heating mats to expose the adhesive side of the mesh and to allow the tile adhesive/screed to pass through the mesh and bond with the substrate below. The mats can be loose laid with the plastic still on to get the layout right and allow you to shift mats as needed to cover the floor however the plastic must be removed, and mesh stuck to the floor to complete the install.
  • Ensure all heating cables and cold tail connections are fully embedded within a layer of flexible cement-based tile adhesive or levelling compound to ensure even distribution of heating.
  • Lay Thermonet underfloor heating mats wire side down to protect the heating cable.
  • Observe and adhere to current electrical guidelines and IP ratings when placing your Thermostat in a wet area.
  • Make sure your underfloor heating circuit is protected by a suitable RCD.
  • Use the provided mat monitor during install and floor laying to alert you of any damage to the cable during this process.
  • Check with your floor manufacturer for compatibility with electric underfloor heating and guidance on maximum temperature especially for soft floor finishes such as carpet or engineered timber.
  • Ensure the installer completes the customer handover form in full before leaving the site and then use this information to complete the online warranty registration within 60 days of installation.
  • Ensure all electrical work is carried out by a qualified electrician and all tests are performed and recorded as per the installation guide. An electrician is not required to lay the heating, however, all the tests and the final wire up of the thermostat must be completed by an electrician.
  • Ensure multiple underfloor heating are wired in parallel into the Thermostat (do not wire underfloor heating mats in series to each other). When using multiple mats check that the total load of the heating elements does not exceed the max load of the Thermostat (16Amps) or if it does ensure that a suitably rated contactor and snubber are wired into the circuit.
  • Ensure the floor temperature sensor probe is installed in a conduit to facilitate easy replacement if required. The floor sensor conduit should be placed centrally between two runs of heating cables to ensure accurate temperature readings.
  • Check with the adhesive/grout manufacturer to ensure suitability and for recommendations on drying times and maximum floor temperatures.
  • Consider using Econoboard Insulation Boards beneath the underfloor heating to boost the efficiency of the underfloor heating system.


  • Never Cut or shorten the heating cable! The heating element is a resistive element and by cutting or shortening the heating cable it is changing the resistance and therefore cause the cable to burn out.
  • Leave any excess cable exposed or coiled under kitchen unit fixtures or inside a wall cavity. All of the heating cable needs to be fully embedded with a layer of flexible tile adhesive and needs to be spaced at least 50mm apart.
  • Allow heating cables to touch or cross over each other.
  • Connect underfloor heating mats/cables in series! Multiple mats/cables must always be wired in parallel.
  • Power up the heating system while coiled or exposed to air as this will cause the heating element to burn out. The electrician is required to test the heating system prior to installation as per instructions in the installation guide.
  • Strain or bond the cold tail connections.
  • Attempt to carry out any electrical work if you are not a fully qualified electrician.
  • Leave your mat monitor on whilst work is not being carried out as the batteries will run flat and the unit will cease to function.
  • Space heating cables less than 50mm apart.
  • Install anything with floor mounted mechanical fixings (Eg. door stops) over an underfloor heating system.
  • Cover an underfloor heating system with solid base permanent fixtures. Air must be allowed to circulate over the floor.
  • Install insulation boards over the underfloor heating.

Please note: This is a quick reference guide only and does not replace the installation guide or regularity literature. It is the installers responsibility to ensure the system adheres to all current electrical, building and other relevant regulations.