We are renovating our kitchen and the contractor will be using wire mesh, scratch coat and Mapei LFT for the floor porcelain tile (24"x24"). A Mapei rep advised to use the membrane, Mapeguard UM as he explained the grout will crack using wire mesh for large format tiles, but my contractor said that since our kitchen area is small (260 sq ft), there is no need to install the membrane, the wire mesh will be fine. Your help would be appreciated.