# thinset thickness for finished measurements?



## ChrWright

lifeisadimensio said:


> If my tile is 1/4", when I'm making allowances for measurements, e.g., where top of floor cabinets will be after adding the tile, should I add anything for the thinset mortar beneath the tile?
> 
> Or, should I assume that the ridges on the bottom of the tile will rest on the sub-floor and the thinset will just occupy the empty space between the ridges, the sub-floor and the bottom of the tile?
> 
> This also tells me, when I press down (or sideways or up) on the tile into the thinset, whether or not I should press until the tile bottoms out or not worry about it.


Yes, you should allow for the thickness of mortar in your calculation. The amount will vary depending on the size trowel you use. 

Trowel size is determined by the tile material, tile size, and substrate. 

If your floor is perfectly flat (and you won't have to make minor corrections with the mortar thickness), you can probably be safe by allowing for 1/8" of mortar. This assumes you're using a 1/4"x1/4" square notch trowel.

What are you measuring for that requires that tight a tolerance for finished height?


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## lifeisadimensio

ChrWright said:


> What are you measuring for that requires that tight a tolerance for finished height?


My real concern is the single lever mixer valve rough-in box in my shower wall. I'm also moving that non-load-bearing false wall to enlarge the shower and don't want the valve protruding in or out too far, thereby causing seal or handle movement problems. 

However, I also have a bathroom sink cabinet, medicine cabinet, and light fixture that I am replacing along with the floor, which is now vinyl tile. The new sink cabinet is much higher than the original to save back pain. I'd also like to use a replacement high faucet with a drop-down spray head. So, I need to know where I have to re-locate the medicine cabinet and light to safely clear the faucet. I'd rather not have to move the light fixture hole again.

Never having done these things before, I do not have a good feel yet for tolerances or sequences. Though I have heard about "measure twice, cut once".

My tile is 18"x18" porcelain. What trowel size (and mortar gap) do you recommend?

Thanks for your help.


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## JazMan

I think you're being way too critical with your figuring, the variations of thin set thickness isn't enough to make any difference in any of the items you've mentioned. (I'll bet you're an engineer) :thumbsup: Tile is an art form.

For the record the recommended cured thin set thickness is a min. of 3/32". A 1/4x1/4 square trowel does not leave a thickness of 1/8", even if the tiles had flat backs, as with natural stone tiles. That answer only works on paper. The ridges are 1/4" wide, but the ridges are not 1/4" high. You're holding the trowel at a 45-50 degree angle, not a full 90 degree.



> My tile is 18"x18" porcelain. What trowel size (and mortar gap) do you recommend?


The typical 18" porcelain will require a 1/2x1/2" or 1/4x1/2x1/4", plus, it's a good idea to butter them too. Can't really know for sure since we have no idea how the substrate is. Grout width? We don't know that either since it depends on the tile's finish look and whether the tiles are rectified or not. Somewhere between 1/8 & 1/4" though.

Jaz


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