Tile Backer Boards
Tile Backer Boards are they worth it?
Tile backer boards are just as important part of the system as the heating cables. Tile backer boards are a 1200m x 600mm foam insulation sheet with a re-enforced cement fascia to both sides, and their main job is to help block the heat generated from the heating cables from penetrating the sub-floor and reflect it upwards into the room.
Choosing the correct board is very easy, quite simply when it comes to insulating the floor, the more you have (the thicker it is) the better it is, you can never have “too much insulation”. Most customers normally choose a 10mm board which is very effective, and some customers use a 50mm board and not bother with the final screed in a conservatory.
Working out how many boards you need is really easy, lets say your room is 3m x 4m, multiply these together = 12m², dived this by the tile backer board which is 1.2m x 0.6m = 0.72m², this gives you 12m²/0.72 = 16.66 boards, round it up and add one for good luck, so you would need 18 boards to cover that floor area.
Insulation plays a key part in the operation and running costs of an underfloor heating system. If you install your heating system on to good quality insulation it will repay you with faster warm-up times, reduced running costs and will give you a good surface upon to tile.
Tile backer boards are normally installed on top of the existing sub-floor, so in the case of a conservatory with a concrete base, these boards would be bonded to the surface then the cables laid on top.
Fastening the boards down is a straight forward process, if you have a concrete sub-floor that is dry and quite dusty we would recommend you prime the concrete with an acrylic primer, such as “Instramac Prime IT AR” solution, get a brush and just slosh it on the floor and cover the whole surface, have a t-break and by the time you come back it should be ready to start to lay the boards. We recommend priming a dusty concrete slab with “Instramac Prime IT AR” because it stops the water being sucked out of the tile adhesive you use next;
The next job is mix the tile adhesive, we use 20Kgs powder flexible tile adhesive and mix it up in a plaster’s bucket, or a gorilla bucket (yellow rubber ones) use a big whisk, same sort of thing plaster’s use. We then spread the adhesive on the concrete using a 4mm notch trowel, we will spread enough to cover 3-4 boards at a time, a 20kgs bag will do roughly 7 boards on a smooth surface.
After you have spread the adhesive lay the boards, start with a full board until you get to the other end, then cut a board to fit, just use a Stanley knife to score the board and snap it. Once the boards are laid down, have a good walk all over them ensuring you squeeze all the air out from underneath and make sure you have a good bond, if there is any doubt use the knife to score the board to make sure it is stuck down, you will most likely have to do this because its rare that a concrete slab wont have any imperfections.
Continue to lay the boards in a brick like fashion, never have two joints the same, once you have done, wash your tools (worst bit) sweep up and that’s it, use some scrim and tape the joints together and that’s it your ready for the cable mat.
If you have a timber floor such as ply you can do the same as above, but make sure you use some mechanical fixing as well such as galvanised screws and washers, alternately just use about 15 screws and washers per board and don’t use adhesive.
It is worth the extra effort and cost, they may seem like an expensive item at first but what they save you with running costs and warm up times outweighs the cost.