Electric Underfloor Heating

Tiles being installed over an electric underfloor heating system

The main objection when considering a tiled floor finish is that tiles are cold to the touch when walked on and therefore not comfortable, unlike carpet or other soft flooring. Whilst tiles may feel cold on your feet when walked on, the actual truth is that tiles will tend to have a surface temperature that is akin to the ambient temperature of the room they reside in. The amount of heat a tile will hold onto over a length of time though will depend on the continuing ambient temperature and the materials that the tile is constructed from.

Electric Underfloor Heating- Tiles

The introduction of electric underfloor heating systems (which maybe refered to as undertile heating systems) have come a long way in the last twenty years, so much so that it is now standard practice to use such a system in many rooms around the house, especially in a climate such as the UK where temperatures in the winter months can have an adverse effect on the temperature exhibited by the floor tiling. The electric underfloor heating systems tend to be available in a kit form which contains everything you need to heat under the tiles in various rooms around the property. Obviously, the size of the room where the undertile heating system is needed will have a huge bearing on the cost of the system and you will need to give your supplier the dimensions of the room so they can work out exactly the quantity of heating wire you will need as well as the type of power supply.

To fit a heating system, your fitter or tiler will generally prepare the substrate first and make any changes that are needed such as strengthening a wooden suspended floor. The surface of the substrate is usually primed first with a proprietary product and the heating system is applied to the floor usually by unrolling a matting based system onto the substrate, or by extending a wire system across the whole surface area of the floor (with recommended gaps between the lengths) The system is usually terminated near to a power supply where a qualified electrical engineer should make the require connections. It is recommended (although not by all manufacturers) that you then overlay the electric underfloor heating system with a suitable latex self levelling compound which will protect the wires from damage when laying the tiles with a metal trowel and make it easier to install the tiles, plus it will distribute the heat more efficiently around the surface area of the floor.

Electric Underfloor Heating- Warnings

It is recommended that you test your electric underfloor heating system prior to installing the tiles if possible, then confirm that the heating has returned to room temperature before starting to install tiles. When the tiles have been laid over the heating system, do not turn on the system instantly as this could shock the installation and cause a failure. it is good practice to allow the whole installation a week to fully cure and reach a full strength, then turn up the underfloor heating system at a rate of 5 degrees a day up to its full operating temperature, allow it to stay there for a time and then turn it down to room temperature equally slowly, this will allow expansion and contraction to occur in the installation at a rate at which all the different substrates and materials can accommodate and allow them to work together. We recommend that you speak to your Tile fixer or supplier for the manufacturers particular recommendations in regards to commissioning various products as there is certain to be slight variations.

Prime the surface with the correct primer first

There is far less risk involved when fitting an underfloor heating system to a solid screeded or concrete floor than for example a suspended wooden floor. The issues associated with suspended floors are that they are constructed with timber which is not a dimensionally stable product and liable to movement and distortion when exposed to differing temperatures, Whilst these problems are real issues, it is possible to fit electric underfloor heating to wood based floors with the correct preparation and commissioning of the system. As always, with a suspended floor you are looking for a good quality timber such as Marine grade plywood, that is of sufficient thickness (15mm) then screwed into existing floorboards at 300mm centres. It is a good ideas to keep your timber inside the room it is to be installed into prior to utilizing it, which is called “pre-conditioning” of timber, similar to what you are expected to do with some laminate flooring before installing. This allows the timber to equalise with the ambient temperature and will negate the risk of future distortion. It is also a good idea to prime with a suitable sbr (styrene butadiene rubber) primer. You should use it neat and apply it to every surface of the timber, this also will protect it from moisture distortion going forward, once installed.

Correct commissioning of the electric underfloor heating system when fitted to a wooden substrate is imperative, make sure that the heating is introduced slowly and allow the timber to become accustomed to the change in temperature as opposed to switching it on full blast and thermal shocking the installation. Using an anti fracture membrane within the installation maybe a good idea to lessen the risk of failure through lateral movement.

Speak to your installer or supplier about utilizing a cement type board instead of timber sheets which is a much safer alternative with less likely consequences from temperature changes, giving a more dimensionally stable substrate. The cement based boards are readily available and offer a water-resistant surface as well as a less risky substrate to install an electric underfloor heating system too.