Underlayment membrane for ceramic tile and stone. Mapeguard UM is a premium-performance, lightweight, waterproofing and vapor-pressure-equalizing underlayment membrane that provides crack suppression for use under ceramic tile and stone installations, for both residential and commercial applications. It is designed to perform over challenging substrates, such as young concrete and single-layer 3/4 in plywood subfloors with joist spacing of up to 19.2 in on center. The unique engineered tri-layered design of Mapeguard UM absorbs lateral stress from the substrate without transferring this force to the tile or stone, which maintains exceptional bonds.