Hi all, I have a room with old plastic/vinyl tiles on top of concrete floor. I want to put laminate on top of those but there is a 2 foot wide, 10mm deep dip in the floor that goes across the whole room. I used MAPEI 3240 to fill it but within 2 days cracks started appearing and it was lifting from the edges. The vinyl tiles underneath are solid. I didn't use a primer because the tiles are not likely to absorb any moisture. Where did I go wrong? Are there any other products that can stick better to those tiles without cracking? Thanks.
The Mapei won't have gripped the vinyl tiles, so you'll end up with a floating 10mm of compound that will likely crack and break up over time and subject to foot traffic. The primer isn't just for moisture-absorbing backgrounds, it's to aid adhesion. In the past I've had to fill over vinyl tiles as a last resort (usually old asbestos-containing 60s/70s-era tiles), in that case I prime with SBR, scatter a few handfuls of washed sand, coat again with SBR and pour whilst it's still tacky.
Sharp sand will do the trick, just be careful that there aren't any large grains (sharp sand can contain anything up to 12mm iirc)
Not saying its the same situation, but when I had to do it it was because the tiles contained asbestos; all the loose tiles or the tiles that came up easy were taken up, but a couple of clusters were stuck solid and started to break up when attempts were made to lift them.
Thanks Rob. I have done it now and it hasn't cracked (10 days now). Removing the tiles would've been the better option but I didn't want to create more work for myself and being a beginner I was worried I would create more problems by removing the tiles.
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