Not all plywood is made the same

There are many types of plywood on the market, but they are not all created equal. According to industry standards, like Terrazzo, Tile and Marble Association of Canada (TTMAC)’s standards, plywood must be Group 1, CC-type, conforming to APA classification and U.S. Product Standard PS 1-95, or CANPLY exterior plywood “Select” or “Select Tight Face” conforming to CSA-0121 standard for Douglas fir, for direct-bond applications.

We have seen many installations completed on non-recommended plywood. For the majority, these installations often result in failure. What we are seeing in these defective installations is that the mortar is well bonded to the tile, but there is little, if any, mortar adherence to the plywood.

While mortars with lower polymer content are recommended for plywood, it is best practice to choose a mortar specifically identified as having improved plywood adhesion. The ISO 13007 Standard helps us properly identify such mortars. This classification is listed on all Technical Data Sheets and on MAPEI mortar packaging as icons. INDUSTRY STANDARDS AND APPROVALS ISO 13007: Classification C2TES1P1

Let’s take a look at the ISO standard for Ultraflex™ LFT™ referring to the table: Ultraflex LFT—C2TES1P1 C = Cementitious 2 = Improved T = Slip-resistant E = Extended open time S1 = Deformable P1 = Plywood adhesion

Some of our other mortars, like Kerabond/Keralastic™ System or Granirapid® System, have the P2 special characteristic. These mortars provide superior bond to plywood.

In order to have a successful and lasting installation over plywood, we suggest using mortars that have at least the P1 special characteristic.

Have a good installation!