Thermopanel Tile Backer boards are specifically designed for two primary purposes:- ---As a first class heat insulation for underfloor heating systems ---As a superior waterproof surface / construction board / to fix wall or floor tiles. The dimensions of each board are 1250mm x 600mm (0.75m²). Each pack includes 15 washers per board. How to work out how many boards you need: To work how many boards you require, work out your room size in m2, then divide that amount by 0.75. For example, for 5m2, the calculation would be: 5 ÷ 0.75 = 6.66, rounded up to make 7 boards. Key Features: ---Tile backer boards are particularly suited to underfloor heating mats and under tile heating cable applications. ---Will accept even the heaviest wall tiles, unlike plasterboard.