Hello Everyone,
I have a question about thinset's ability to compenset for slight variations. I know I can't use it to fix major issues, but what about very minor ones? We've just prepped our kitchen floor for a tiling project, and we're about to begin putting down 1/4" cement board. When we were trying to clean the floor for this, we found out that only portions of the vinyl/laminate tile would come up, the rest has basically merged with the 3/4" plywood beneath it (the vinyl/laminate has no compression, so we've decided to just go right over it since there will be CBU over it). This means that in some spots we have areas that are slightly more than 1/16" different (lower) than most of the floor. Can thinset handle that difference? Or should I put down some floor patch first?
Thanks!

You can handle it with thinset. Thinset thickeness can be varied by either the size notched trowel you use or by how much angle you put on the trowel as you spread the thinset. If needed, you can mix the thinset thicker or thinner for particular areas of the floor.

While you can use thinset to level the backerboard and the tile, it will be easier to work on leveling the thinset that is used to adhere the backerboard. This will give you a more level surface to lay tile and make the tile install easier.

EricH:

The way you would remove that black backing paper from the plywood is with a 4 inch flooring razor scraper, like this one:

http://www.northlandconstructi...g/06-1300%20copy.jpg

Both Gundlach and Crain make good quality tools like this, and you can buy them at any place that sells flooring installation supplies, but the A. Richard company makes a cheap one that Home Depot sells as a "wall paper scraper".

If you decide to buy one of these tools to remove that black paper stuck to the plywood, take note that the blade will be installed backwards at the factory so that people don't cut themselves handling the tool. Once it's sold, the owner should reinstall the blade properly. The blades are super sharp, and you'll go through a few of them, so buy some spare blades too.

If you trowel thin set over your plywood and set your cement board in that, then I expect the bed of thin set will be thick enough that the paper won't matter.

However, I'm a perfectionist, and for the $10 a "wall paper scraper" from Home Depot is gonna cost, if it wuz me, I'd probably shave the black paper off before putting the cement board down.

PS: you should also be aware that linoleum tiles were commonly installed with a paste made by the Roberts Company called "Linogrip 55". Because Linogrip 55 is a paste, it doesn't have a chemical cure, but dries by evaporation of water, just in the same way that muck transforms into mud. Linogrip 55 dries to a dark brown colour, so if the adhesive holding your old linoleum tiles down is brown in colour, it's probably Linogrip 55 and even after 65 years, it'll still dissolve in water.

This message has been edited. Last edited by: Nestor,

A variance of 1/16 of an inch is nothing. The thinset will do fine. Floors often vary by more than that, and thats where you can run into problems. A big gully of 1/4 inch or more is when you'll run into problems laying the tile. Slab floor homes need repair then, or perimeter foundation homes might have an issue that needs addressing before the tile work gets done.

Thanks for the answers, they came in handy (I completed the CBU install over this past weekend).

Nestor:
There was no black paper that I could tell, just a black adhesive layer that was beneath the vinyl/linoleum. The house was built in 1955,and that was the bottom-most layer, so its possible that it was the Linogrip you had mentioned (it was black, rather than brown though). We had originally tried removing it all around February, even using a sawzall and scraper attachement, but it wasn't budging. Fast forward to this wonderful heat we're having and up it came with a little elbow-grease!

Sorry. I thought you had mentioned that you were removing "linoleum tiles" and some had remained stuck to the plywood.

Linoleum tiles are constructed much the same as sheet "linoleum" with a vinyl wear layer and paper backing. Normally, the paper backing on linoleum tiles often does stay stuck down to the floor when you remove the tiles.