Schluter Unmodified Thin Set Mortar White 50 lb Set50w

Unmodified Thin Set Mortar White is an unmodified thin-set mortar made for Schluter membranes. On paper that is ANSI A118.1T. A 50 lb bag gets you 150 sq ft with an 11/64" DITRA trowel bonding the membrane down. Setting tile on top is a different number: 60 to 70 sq ft with a 1/4" x 1/4" notch setting tile over DITRA. You get 20 to 30 minutes of open time. Pot life is 2 to 4 hours. Keep traffic and water off for at least 24 hours. Grout after at least 12 hours at 70F, longer when it is cold. Back-butter anything 12" x 12" or larger. It is approved over DITRA over concrete or gypsum, KERDI over gypsum board and cement board, and tile over either membrane. Keep it off plywood and OSB. It will not bond DITRA to a wood subfloor and Schluter say so plainly. Also not particle board, luan, hardwood or dimension lumber. This is the unmodified mortar the DITRA instructions call for when setting tile on top of the membrane. The rule catches people out: modified goes under the membrane on a wood subfloor, unmodified goes over it. On the shelf in Mississauga and Barrie if you are picking up tile anyway.