Hi, We have a got a flat on 3rd floor in a purpose built. We just noticed our bathroom floor board got damaged with water and it's almost to be replaced. This time we are looking to get tiles but please advise if we replace chipboard with hardieback cement floor boards and then tile over. Or do we need ply first and then hardieback cement floor and then tiling. We will be ripping whole bathroom so have the option to replace the floor altogether. Please advise. Thanks Kaps
Lay ply, or replacement chipboard, first - at least 18mm. Being cement board, Hardiebacker board is strong in compression, but weak in tension so it will crack if you put any bending load on it, such as your weight unsupported between joists.
I actually have a floor made from 12mm Hardie Backer - not advised however with underfloor heating and joists at 300mm, it works fine! As for the OP - 19mm ply then 6mm backer or if you can get it, 19 or 22mm Hardie Floor in 2400x500 planks which can be tiled on directly. https://www.buildworld.co.uk/mercha...-x-500mm-x-19mm-hardiefloor-flooring-bw-17349