Bostik Flexacryl Instant Repair for flat roofs is a flexible, single coat waterproofing compound that offers immediate waterproofing over most conventional roofing substrates. It can be brushed straight from the tin onto substrates such as old roofing felt, asphalt, bituminous roof coatings, cement, concrete, lead work, metal, brickwork, slate and rigid PVC. Its long-lasting formula makes it ideal for emergency repairs or general waterproofing of flat roofs and can be applied to wet or dry surfaces.