The TrueCable (10W/m) thin underfloor heating cable kit is designed for installation on wooden or concrete floors under floor tiles. *Please check that your floor finish is suitable for underfloor heating before purchasing. The TrueHeat underfloor heating cables are available in a wide range of sizes and an unlimited amount of heating mats can be used to heat any floor area Selecting the Correct Cable To select the correct cable you need to know a few things, Free Heated Floor Area? Primary or Secondary Heating? Once you know the free floor area you can move on to selecting the correct cable for yourself. Each cable has a minimum and maximum square metres, these are what the cable would cover at 100w/m2 being the smallest measurement up to 200w/m2 being the highest measurement.