Water Based Polyurethane Waterproofing Coatings MonoProof WPU is a flexible, single component aliphatic liquid membrane. It cures to a permanently flexible seamless membrane that has good adhesion to a wide range of substrates unlike more traditional bitumen based products. The coating is crack-bridging, does not readily embrittle with age, exposure to ultra violet radiation or weathering, and hence it does not crack or craze due to its flexible properties. It is elastomeric and hence not adversely affected by extremes of temperature.