From the Floor Up

“Medium Bed Mortar” Changed to “LHT Mortar”

Posted by Daltile Team on Jan 27, 2016 10:30:00 AM

Understanding Changes in the Tile Industry Series

This year, when the Tile Council of North America published its installation handbook, there were a few changes. What do these changes mean for you? Clear up any misunderstandings and stay on top of the industry with this review of the changes to what you know as medium bed mortar.U notch trowel with LHT mortar

Why Switch the Name?

The switch to “large and heavy tile mortar” comes because of the confusion over methods and mortars for large format or heavy tile. Medium bed mortar was designed to support a larger, heavier tile, especially because the edges were prone to slumping.

Over time, installers, contractors, and tile manufacturers began thinking of medium bed mortar as a means to even up substrates and ease into floor height transitions. It wasn’t long before the term “medium bed method” was flying around and specs began to employ it.

This type of mortar simply wasn’t designed to be a truing or leveling product. It is a direct bond adhesive, not a method for installing tile.

In short, the change in name supports what “medium bed”—now “LHT mortars”—are and aren’t designed to do.

Anything Else I Should Know?

LHT Mortar is ideal for installing . . .

  • tiles with one side greater than 15"
  • tiles heavier than 5 lbs.
  • ungauged tiles (Indian slate)
  • tiles iwth allowable warpage (plank tiles)

One thing hasn’t changed: LHT still needs a thicker bond coat to support its size and weight properly and meet mortar coverage requirements. But the thickness of that bond is changing. Previously, the thickness of the mortar after the tile is embedded was to be 3/32” up to 3/4”. The TCNA now specifies 3/32” to 1/2". Industry professionals felt this was a more precise and accurate range for large and/or heavy tile.

Additionally, though there are no specific notes in ANSI or ISO standards about LHT mortar, this is expected to change very soon. The Materials and Methods Standards Association researched and drafted proposals that other standards committees will eventually adopt.

What Now?

Aside from calling the mortar something different, what does this mean for you? It means three things:

  1. If you have been using LHT mortar to correct substrates, you’ll have to make an adjustment. The mortar is not designed for this purpose.

  2. Plans and specifications referring to “medium bed method”, “large and heavy method”, or use of medium bed mortar to correct substrates or create slopes on floor heights no longer meet industry standards and will have to be amended.

  3. Installers will now have better information and support when they run into conflicting specifications and recommendations.

Daltile is consistently working to make sure our products and specifications meet or exceed industry standards in a timely fashion.

Join us next Wednesday for a look at another change to the tile industry: curbless shower methods.

If you have questions or observations, please leave them in the comments below. We’d love to have a conversation about it.

Topics: How to Install Tile, Industry

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