Underfloor heating frequently asked questions
Below are a selection of questions we are regularly asked by our customers.
They cover the most common queries we hear and should help out in most situations. If your question is not answer below feel free to call our highly experienced team, using the number at the top of the screen, who will be more than happy to help.
Heating Mats:
Heating mats are the same cable as the loose cable kits (2mm loose heating cable rated @10 watts/m) already spaced out for you and attached to a fully adhesive mesh backing. Our heating mats come in 3 wattages:
200 watts per square meter
this is the most powerful type of heating mat. It can be used beneath tiled or stone floors and is recommended for high heat loss areas such as conservatories. It should also be used where laying onto a concrete floor when not using insulation boards. The maximum size of mat on 1 thermostat is 18m2
150 watts per square meter
this is a mid-range powered mat which is suitable for most applications which can be used as a primary source of heating beneath most floor finishes. It should be noted that finishes such as Kardean or Amtico have a maximum of 150w per meter. The maximum size of mat on 1 thermostat is 24m2
100 watts per square meter
This is the lowest powered mat which is suitable for taking the chill off cold tiles – it is not suitable for a primary heating source. The maximum size of mat on 1 thermostat is 30m2
Heating mats are for use on a finished subfloor such as concrete screed or plywood and we recommend they are encased in either a flexible tile adhesive (if laying tiles) or a flexible levelling compound if laying any other floor finish.
Heating Cables:
The loose heating cable is rated at 10 watts per linear meter and is the same cable used in the heating mats. The cable comes on a drum and spacing must be manually measured (full instructions on how to do this are included in the kit).
In Screed Heating Cable:
Must be encased in the finishing screed of the concrete floor (usually a minimum of 65mm as per Building regulations) with a minimum of 20mm of the screed above the cable. The same maximum outputs are recommended for the in-screed cable, that is, up to 200watts/sqm beneath tiles / stone and 160 watts/sqm beneath all other floor finishes.
The mats are 500mm wide and come in different lengths to suit the size of the room you require. For instance if you require a 4m2 mat kit, it would come on a roll of 8m2 long by 500mm wide. This covers 4m2. You roll out the mat and cut it when you reach the end of the room then flip it over and come back the other way.
Our heating cables are 2mm thick, but you need to allow for your tile adhesive (5mm), your tile and any insulation board used.
Underwood – 140w per meter
Under Tiles / stone floors – up to 200w per meter
Under carpet or lino – maximum of 150w per meter
If you would like to heat a standard room which is well insulated 150 watts or greater is required. If you are heating a conservatory, which is considered high heat loss or a room with lots of fixed furniture such as a kitchen then we suggest 200w. 200w by nature heats up faster than the 150w so if you can use it then you may as well have the most powerful.
This means that no further insulation products are required saving both money and installation time. Another big advantage of warm water underfloor heating over electric systems in large areas is that most houses will only have a 100amp fuse rating meaning that a whole house system could possibly draw too much current.
This depends on a number of factors including room height and insulations levels in floor and walls, but if insulation boards are used (blueboard or Heatstore tile backer boards for tiles – depron or blueboard for wood) then the system should heat the room.
The system always works best if used with suitable insulation boards as this prevents the heat from going downwards instead of upwards. We understand that not everyone has the floor height to install a board so in this case you could use Thermacoat thermal paint, which does not raise the height at all.
Yes, our range of thermostats will switch 15amps so any combination of mats or cables can be connected as long as the total load does not exceed this. If you would like to switch a larger area with 1 stat then you can use a contactor to switch the load, please call for more info on this.
When using more than two heating mat / cables to connect into 1 thermostat it may be a little tight to get all the cables into the thermostat terminals – in this case you can use a junction box to connect them which can be positioned on the wall behind a blanking plate or similar.
The floor will reach a temperature of approx 28c and will never feel too hot too touch
You should aim to cover between 80-95% of the free floor space of the room. Covering less than 80 % of the FFS means you will end up with cold spots on your floor. We recommend that you measure the intended area to be heated and remove 10% of your total measurement to ensure that you don’t order too much.
