Can thinset be applied too thick so as to cause a problem with cracking tile?

Yes, thinset should be set with a notched trowel that is dictated by the size/type of your tile. If thinset is too thick it will take a very long time to cure and cracking tiles can result when you walk on the tile. How big is your tile, what type?

The "tile" is actually travertine stone--cut to fit over a wood curb. The approximate length and wide of the cut stone is 6" x 10"

I would use a 1/4x1/4 notched trowel

The thinset has been applied in thicknesses as much as 3/4" thick. It is these areas that the travertine stone has cracked and buckled. I'm just exploring ideas as to "cause and effect."

If that job was done by a pro you have recourse, it was improperly laid. Thinset means THIN set and I have never heard of anyone laying tile on 3/4". If more height were needed the sub floor should have been built higher before laying the tile.

Thanks for your time... I appreciate your help.

Yes. Thinset should be the depth of the notched trowel you are using. The article what is thinset on icreatables.com states that up to 8" tiles use a 1/4" x 1/4" x 1/4" notched trowel. This will cover 90 sq. ft. of floor and tile. 8" to 12" tiles - 1/4" x 3/8" x 3/8" notched trowel. This will cover 60 sq. ft. of floor and tile. 12" or larger tiles - 1/2" notched trowel. This will cover 60 sq. ft. of floor and tile. 12" x 1/2" notched trowel. This will cover 45 sq. ft. of floor and tile.

Thanks.

The thinset has been applied in thicknesses as much as 3/4" thick. It is these areas that the travertine stone has cracked and buckled. I'm just exploring ideas as to "cause and effect."

Travertine is a fairly soft stone. Natural stone isn't quite like other tiles. It requires a higher standard of allowed deflection - L/720 - actually twice that of ceramic tile.

So ... essentially if there is any "give" underneath, your stone tile will crack. This is why most stone installations require 3/4 plywood PLUS an additional 1/2". BUT... stone tile has no clue what is under it - all it knows is if it bends at all, it'll break. So there are the "standard" ways to get the job done, and then there is whatever will actually work.

Our master bath uses a combination of 3/8" travertines on the walls and another soft multi-colored stone called mocha onyx for the floor - also 3/8". We only had room for a single layer of 3/4" plywood. So we sistered all the joists underneath, and added additional vertical supports along the joists to provide a very low deflection. For only an additional 1/8" Wedi subliner dry provides anti-fracture protection from any cracks below, from transferring upwards.

If your thinset is too thick, then that could be a problem. But IF the area UNDER that thinset is too flexible then that is a real issue. You could TRY using an antifracture membrane like Wedi or Ditra. IF that solves it then you are pretty lucky. If not... your ONLY way to stop cracking is to reinforce the floor underneath so that it doesn't give.

GOOD LUCK!

Oh... and YES - if the thinset is too thick then it can shrink up and... cracked tiles. If you are lucky then that is your root cause. It's easier to fix that then stuff down below.

Welcome jefferson

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Thanks

Chuck