PROVA-FLEX is a durable, lightweight uncoupling membrane that provides crack isolation protection to concrete or wood substrates. The underlayment consists of three layers: a top layer of woven polypropylene mesh, a central sheet of polypropylene, and a bottom layer of non-woven polypropylene. The top layer provides a mechanical bond between the cured thin set and tiles, and allows for the efficient spread of thin set mortar; the central layer includes hollow studs for holding modified thin set mortar; and the bottom layer, which is secured with a polyolefin-based adhesive, provides Shear Stress Control by neutralizing stress caused by substrate movement. This underlayment is lightweight and is an easy-to-install alternative to backer board.