Expert Advice

Expert Advice for Large and Heavy Tile Installation

22 Nov

Posted by
Tom Plaskota
Technical Support Manager

Expert Advice for Large Format Tile Installation

As the popularity of large and heavy tile (LHT) continues trending upward, this is a good time to review the newest technology on the market for LHT mortar.

The “Setting Materials Selection Guide” in the 2015 TCNA Handbook introduced the term LHT mortar to replace “medium bed mortar” to bring clarity to the specification process.

The clarification set forth five important definitions and guidelines for LHT mortar:

  1. “Large” tile is still defined as having at least one side 15” or greater.
  2. “Heavy” tile weighs over five pounds per square foot.
  3. The bond coat thickness after the tile is embedded is now intended to be 3/32" to 1/2”. 
  4. When setting such tiles, larger trowels are needed “to apply enough bonding mortar to achieve mortar coverage requirements.”
  5. The TCNA Handbook also clarified this limitation: LHT mortar is “designed as direct bond adhesives and are not intended to be used in truing or leveling underlying substrates.”


No Slump, No Shrink

Installing large and heavy tile may cause mortar coverage and bonding challenges. The new TEC® PermaFlex® 300 LHT Mortar is a dependable mortar for installing large and heavy floor tile. Ideal for interior and exterior use, it can be used for bedding thicknesses of 3/32”- 3/4” so large tiles stay in place with the proper coverage needed. It can be used for the installation of porcelain tile, ceramic tile, quarry tile, cement tile, pavers and high bottom lugged tile. PermaFlex® 300 LHT also can be used for the installation of non-moisture sensitive natural stone with the understanding that all natural stone should be tested to be sure discoloration does not occur.


Workability, Coverage

PermaFlex® 300 LHT Mortar offers good workability and helps overcome irregularities in tile thickness.

Back-buttering is usually a good idea to achieve 100% coverage for large and heavy tile, especially with natural stone, but it does add installation time.

We can tell you that with TEC® PermaFlex® 300 LHT Mortar coverage will vary with condition of the substrate and with the selection of the proper trowel size. In turn, the required trowel size will vary with the tile size, type and substrate uniformity. Manufacturing guidelines help a contractor choose the trowel size that will help ensure 100% coverage, making back-buttering unnecessary.

In the end, every project is unique. The advent of this LHT mortar technology brings more uniformity to the installation process and peace of mind for everyone involved.

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