How to tile over old vinyl-tile adhesive?

burgie · 08-17-2009, 01:39 PM

I would like to know what I should do to tile over the old linoleum tile adhesive (thin black, tarry looking stuff), short of removing it. In one small bathroom I have tried covering it with 2 coats of KILZ sealer. I'm not sure that the thinset will adhere to the KILZ and want some help before I make any (more?) mistakes!

In searching other online forums I have seen recommendations to remove the adhesive, and recommendations to leave it in place. My preference is to seal it instead of removing it, since it may contain asbestos.

poppamole · 08-17-2009, 04:10 PM

if you have the room, screw down 1/4 in cement board right over the linoleum, then lay tile over that. wonder board and Durock are some brand names. good luck with it

Nestor_Kelebay · 08-18-2009, 07:08 PM

If you hadn't painted over it with the KILZ, then you could just mix your thin set powder with straight additive (pronounced "adhesive"), and tile right over that black asphaltic adhesive.

Now that there's a coat of KILZ over it, you should check to see if the KILZ is sticking well. Try scraping or peeling it off, and see if it puts up a fight to stay on. If it does, then it's sticking well to the black adhesive, and I'd leave it in place.

What you need to do is trowel down a bed of thin set and lay the cement board in it, and screw the cement board down. This layer of thin set will fill in any gaps between the existing floor and the cement board that would flex if there were no thin set between them.

For floor tiles, rather than use a cement board like Wonderboard or Durock, you're better off using a product called "Hardiebacker board" that comes in 1/4, and 1/2 inch thicknesses. Hardibacker is whitish in colour and is much stronger than the traditional grey cement based boards like Wonderboard.

I'd find out if Hardiebacker comes in 3/8 inch. I've never done any floor tiling, but I've set way more than my fair share of wall tiles.

Then you set your ceramic tile over the Hardiebacker board.

JALEXED2 · 08-20-2009, 06:53 AM

I would be wary of using any kind of adhesive to secure your underlayment boards. At some time in the future, someone will want to replace your tile and will probably want to get down to the original flooring. Any kind of adhesive will just make the job ugly. As previously recommended, lay down an underlayment panel and screw it down to the flooring and don't be bashful about using a good number of screws. Any deflection in the underlayment will result in cracks in the grout over a period of time. Many installers don't want to deal with the original flooring and secure underlayment as a safe way to install without customer followup problems.