6mm PrePrimed Tile Backer is perfect for strengthening timber floors before tiling. Due to their fibre cement construction, they prevent tiles and grout lines cracking by removing the flex in timber floors caused by footfall. Slim 6mm boards provide the same strength as 15-18mm plywood and so reduce the step into the tiled area. NoMorePly 6mm PrePrimed Tile Backer is also water resistant, unlike plywood which weakens when damp. Plus, its covered with a lifetime guarantee.