How do I fix insulating backer boards to concrete floors ?
Prior to the fixing of insulating backer board, all traces of existing finishes should be removed back to the concrete substrate. The floor should be level and dust free. New concrete or screed should be well cured prior to the fixing of insulating backer board. A good proprietary flexible floor tile adhesive (not solvent based) should be used for boards of 6mm or 10mm depth. Apply the bed of adhesive to the floor using a notched trowel. Any slight depressions in the concrete substrate will normally be taken up with the thickness of the adhesive. Boards should be thoroughly bedded, ensuring that no voids remain beneath them. A waterproof joint can be made by running a bead of silicone sealant along the edge face and butting the adjacent board up to it. When the tile adhesive is dry, tape board joints with a fibreglass reinforcing scrim tape.
