Summary: Learn how to install underfloor heating, install an underfloor heating cable system and fit a mesh mat underfloor heating system.
* Notifiable project requiring Building Control approval.
Underfloor heating has several advantages over other heating systems: it is quiet, does not need radiators fixed to the walls and distributes heat evenly across a room. On the other hand, it can be slow to heat up and cool down, and requires disruption to the flooring to install. Also the type of flooring can affect the performance of an underfloor heating system. When choosing your supplier, aim for one that offers technical support.
For DIY installation there are two electric systems available: heating cable and mesh mats. Both systems can only be laid under ceramic floor tiles.
After the cable has been laid and a temperature probe installed, tile adhesive is spread over the cable and the floor tiles are laid. A thermostat positioned on the wall controls the system. If the total power consumption is less than 3kW, this can be wired as a fused spur on a ring main circuit. If the total power consumption is greater than 3kW then it will need its own separate circuit fitted with a 30 or 32 amp MCB at the consumer unit.
Mesh mat underfloor heating is the easier of the two systems to install. The cable is in parallel loops but woven into mesh mats. The mats will be 500mm (19 ½ in) wide but can vary in length from 1m to 20m (about 3ft to 65ft). When calculating the amount of mesh mat needed, the coverage is normally based on 90% of the floor area. Therefore a floor area of 10 sq metres will require 9 sq metres of mesh mat.
A thermostat connector will be fitted to each end of the cable. In the centre of the room a temperature sensor is positioned and covered in flat oval conduit, which is connected to a wall-mounted thermostat controlling the heat output.
The type of floor you have also influences how you lay the mesh mat. A suspended timber floor needs to have cement thermal boards laid over it to direct the heat upwards, so laying the mesh mat on a concrete floor is easier and this is the method we look at here.
Firstly, plan the position of the FCU and the wall-mounted thermostat.
Cut the mesh matting so it can be turned and rolled out in the opposite direction.
Leave a 50mm gap between the mats.
Press the mat into the tile adhesive with a gloved hand.
Cover the mesh mat with 5mm of tile adhesive and lay your ceramic floor tiles on top.
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