Not all plywood is made the same


Normand Sabourin

 October 2, 2020. 5:23 PM

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.


  • ISO 13007: Classification C2TES1P1


Let’s take a look at the ISO standard for Ultraflex LFT referring to the table:

Ultraflex LFTC2TES1P1

C = Cementitious
2 = Improved
T = Slip-resistant
E = Extended open time
S1 = Deformable
P1 = Plywood adhesion 


Some of our other mortars, like Kerabond/KeralasticSystem 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!


Products mentioned in the article

Ultraflex LFT
Ultraflex LFT
Premium, Large-and-Heavy-Tile Mortar with Polymer Ultraflex LFT is a premium, nonsag, large-and-heavy-tile mortar and thin-set mortar…
Granirapid System
Granirapid System
Premium, Rapid-Setting, Flexible Tile Mortar Granirapid is the industry’s first and most flexible, high-performance, fast-curing mortar…
Kerabond/Keralastic System
Kerabond/Keralastic System
Premium, Flexible Tile Mortar Kerabond/Keralastic System is a high-performance, two-part system: Keralastic , a second-generation…


Normand Sabourin

Normand Sabourin

Normand Sabourin was a tile setter for 15 years and a ceramic specialty contractor for 5 years. He started with MAPEI in 2015 as a Technical Representative and now serves as Assistant Manager of Technical Services for the FCIS and TSIS lines. In the areas of Montreal and Quebec City, Normand provides training to installers, contractors, trade schools, suppliers and salespeople on the various products we offer.


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