How To Size My Heating Mat

The important thing to know when ordering an underfloor heating kit is that you can't make the cable shorter, even if you have some knowledge on how to terminate a cable. Cutting a cable will increase its heat output, which will in turn damage the cable overtime. However, you can cut the fiberglass mesh without issues.

So when ordering a DIY Works Kit, it is important to size your heating mat correctly. If in doubt, we highly recommend you to use a smaller size heating mat.

Step 1: Draw the plan of the room

First step is to draw the plan of the space you would like to heat. You can either use a tape measure and manually draw the room. Or for the more tech-savvy, you can use an app to do this work for you.

Step 2: Don't forget to remove fixed furniture

Once the room is drawn, calculate the area and remove the area that will be taken by items where you do not heat (for example, shower, toilet, built-in wardrobe, kitchen island, pretty much anywhere that will have a permanent fixture over it where there is a risk of drilling into the floor).

Note that while it is technically feasible to heat in the shower area, we don't recommend it for several reasons:

  • The tiles get heated as you taking a shower.
  • Depending on the design of the bathroom, the shower screen can be screwed down to the floor, with a risk of damaging the cable.
  • Laying down the mat can be difficult if there is a strip drain that separate the shower area to the rest of the bathroom.

Step 3: Choose the smaller size

For example, if your calculate a heated surface of 3.8 sqm, use the 3.5 sqm mat.