Hi - I am preparing a floor on which I want to lay vinyl tiles. I've taken the old tiles up. The floor underneath is concrete but there is a thick, uneven layer of old tile adhesive (black and bituminous looking) on top of it.
Can I use a self levelling compound on top of this or will I have to remove it first? If I do have to remove it, any tips on the best way of doing so without wrecking the concrete underneath?
Its really not wise to use self leveller over adhesive. It has been done by painting the adhsive with latex solution first and even undiluted PVA adhesive but, and it is a huge BUT, the Self Leveller needs to be fixed absolutely 100% perfect to the floor surface to give a new floor of any kind a chance and if any part of the existing adhesive is at all vulnerable it will affect the new screed which in turn will affect the new tiles. In other words the new surface is only as good as the existing surface regardless of what you put in between. Its not advised at all.
Take a look at the project on the website called removing vinyl tiles. A hot air gun, set to warm, will make the adhesive a little easier to get up using a scraper.
I have a similar situation - I've taken up the old lino tiles in my kitchen and there is a thin bitumenous glue layer left. I've tried the heat gun/scraper combo but it took about 30 mins to clear a few square inches and at that rate it will be winter before I finish.
I checked the 'removing vinyl tiles' project - [quote]If the adhesive is particularly well stuck[/quote] The stuff I am trying to shift seems to fit the category, and the floor itself is nice & flat so there is no need for levelling compound.
Now, as there will not be a very thick layer of adhesive my concern is that the tiles and their adhesive will 'float' and break up so a) will the PVA option be any good b) should I really stick with tying to remove an incredibly stubborn 30-year-old glue layer or c) would it be a reasonable idea to lay a thin plywood layer (firmly screwed into the concrete floor) as a new base to tile on?
I'm about to lay self adhesive vinyl tiles in same situation as coops666 having previously lifted old tiles stuck down with bitumen. I'm going to fix 6mm ply board first and then tiles on top. I was advised to seal the ply with PVA solution first - would that be sufficient to give good adhesion?
I renovated the kitchen in our 1940's house 18 months ago and came up against a similar problem. We wanted to lay a ceramic tile floor, and after removing the carpet tiles, and vinyl tiles underneath, we came up against an uneven concrete base with a bitumen-like glue that was difficult to remove. After scraping the floor using a heat gun, I sealed the remaining adhesive with PVA before laying the self levelling compound.
As thedoctor pointed out, this is not necessarily a good idea - and thankfully because of delays with the electricans and plasterer which prevented me from laying the ceramic tiles, I observed the self levelling compound debond and crack extensively (especially over a one patch of bitumen - there was a definite correlation between residual adhesive and debonding). I contacted the manufacturers of the self levelling compound and they directed me to use their own sealant (a methacrylate based compound). After bolstering up the cracked self-levelling compound I tried their sealant - before relevelling the floor. I waited a week before proceeding, just to make sure, and again the cracks appeared - and the manufacturers really had no suggestion as to what to do.
I tried solvents, and scrapers, and found it very difficult to remove.
In the end I hired a concrete planar and basically took off the top 1 or 2 mm of the bitumen impregnated concrete (a very dirty job that creates a lot of dust - so seal all the gaps in the doors to other rooms). I got a good bond this time - and 18 months later my ceramic tiles are still solidly in place. My advice would be to consider this as an option.