In 1987, a new product cat- egory was launched in the North American Tile industry called “Uncoupling Membrane.” The product – an orange membrane – was made of polyethylene, ribbed in one direction and had a poly- propylene mesh heat-bonded on the underside. This product was only 3/16” (4.5 mm) thick and 3’ 3” (1 m) wide and only weighed 45 lbs. (20.4kg) for a 323 sq. ft. (30 sq.m.) roll. Surprisingly, one of the most popular uses of this very flex- ible and non-rigid membrane was over plywood substrates, includ- ing over a single layer of ply- wood. In 1999, the first detail for a “Proprietary Membrane” with double layer of wood subfloor on 24” (600 mm) on-center (o.c.) joist spacing was introduced to the TCNA Handbook (F147). Then, only two years later in 2001, a second detail was added to the Handbook for going over a single- layer plywood floor on 19.2” (480 Uncoupling membranes methods and standards: a timeline By Dale Kempster, Director of International Technical Network of North America, Schluter Systems LLC TECH TALK –––––––––––––––––––––––––––– F147 F148 90 TileLetter | July 2019