disclosed herein are polyurethane compositions specifically adapted to produce non - porous membranes exhibiting waterproof and water vapor transmissible characteristics . the membranes can be produced as free standing products or can be produced as coatings on porous substrates to confer similar properties to such substrates . also disclosed are coated fabrics and fabric laminates utilizing the membranous coatings of the invention and exhibiting waterproof and water vapor transmissible characteristics . such coated fabrics and fabric laminates find utility in the fabrication of tenting , rainwear and other garments where waterproofness , coupled with breathability , are important features .