A single part fibre reinforced self-smoothing floor underlayment. It is suitable for use from 3-50mm thickness in one application without the need for additional granite chippings. The product is suitable for levelling a variety of substrates including concrete, screed, flooring grade asphalt terrazzo and existing quarry and vinyl tiles. It is ideal for use with undertile heating mats where it may be used to cover the wired elements, providing a level substrate to tile to and also protecting the heating elements during the fixing process. The product is suitable for use on timber floors which must be overlaid with a minimum 15-18mm thick WBP or Marine grade plywood screw fixed at maximum 300mm centres to both joists and existing boards. The plywood should be primed with neat Norcros Prime Bond which should be allowed to dry prior to application of the levelling compound.