Hi
There are lots of threads on the 'Net about removing the old tar-like adhesives from concrete prior to tiling. But can I tile directly on top of it without removing it first? A mate suggested I need to apply a silicone based self leveling compound first, but I reckon when I have all the tiles out the floor will be very level anyway, so will this act as a sealer?
What I have is a very thin layer of tar-like adhesive/dpm between the concrete and the tiles (very brittle vinyl/lino like), which come off almost on their own, leaving the thin old tar stuck on concrete.
Not sure if this helps at all - the pattern left on the tar suggests it was applied or washed onto the concrete floor with a mop or a similar tool, which I guess explains why it is so thin.
I think I will discover cracks in the floor when I take all the tiles off (the external walls have had major cracks repaired in the past). Once I fill those with repair cement, will the same sealant act as the dpm over the filled cracks?
Any help much appreciated!
Thanks!!

The tile you describe sounds like a thermoplastic. These tiles are fixed with a bitumen based adhesive known as ATA. I would recomend you remove as much residue as poss. A heat gun and scraper might help. What is the sub-floor?

Hi. I remember reading about some BAL two part self leveller that is supposed to stabilise this sort of substrate once the floor has been scarified and all loose stuff is removed, BAL or Mapei tech support could be a starting point, good luck Mate, let us know how you go on Steve aka ozboz

Cheers Steve, I would like to know more about this. I have the same problem on my current job ATA residue.

Hiya Phil, here is a link BAL Adhesives - Products - acrybase Im sure that will be an ok product for your present job, give em a call Ok seeya Steve ( gotta be better than blow lamps !!)

wick's high performance laytex did it for me . did 30 mtr 1 year ago no problems . but not on walls .

Thaks everyone for the replies. Sounds like whatever I do it will not be an easy job!

To Phil - The concrete floor is about 4-5cm think and I think the subfloor is just sand. There is a photo here:



Thanks again!

On many jobs (including my own bungalow) I have encountered the same problem. I have solved it by doing the following-

1. Remove old thermoplastic tiles and scrape off any lumps etc
2. Coat floor in a SBR coat
3. Mix up a cement (I have found rapid set best) and SBR slurry so it is the consistency of pancake mixture
4. Pour on floor, then spread evenly by large brush or roller.
5. Wait for it to dry, and repeat if needed
6. SBR coat this dried layer(s)
7. Apply rapidset tile adhesive prior to fitting insulation board, or just apply tanking membrane directly to the last step (4). If you are not using UFH, or not fitting in a bathroom wetroom scenario, then just tile on top of the dry slurry coat.

Many threads on here mention slurry coat, and I tried the grinding/ scraping .............. alot of effort, and it never really solves it.

It has been fool proof for me, and no problems to date.

I would normally use SLC 3mm thick like Ardex Arditex latex, or Tilemaster Levelflex (mix with water), or Ball Stopgap Greenbag + 128, these will all cover the bitumen adhesive successfully.

Ardex RS leveller, Mapei Latexplan amongst others will neutralise the base once yu have removed as much as humanly possible and all the loose is gone

Originally Posted by blocko

On many jobs (including my own bungalow) I have encountered the same problem. I have solved it by doing the following-

1. Remove old thermoplastic tiles and scrape off any lumps etc
2. Coat floor in a SBR coat
3. Mix up a cement (I have found rapid set best) and SBR slurry so it is the consistency of pancake mixture
4. Pour on floor, then spread evenly by large brush or roller.
5. Wait for it to dry, and repeat if needed
6. SBR coat this dried layer(s)
7. Apply rapidset tile adhesive prior to fitting insulation board, or just apply tanking membrane directly to the last step (4). If you are not using UFH, or not fitting in a bathroom wetroom scenario, then just tile on top of the dry slurry coat.

Many threads on here mention slurry coat, and I tried the grinding/ scraping .............. alot of effort, and it never really solves it.

It has been fool proof for me, and no problems to date.

What sort of drying times, after SBR coat? after slurry coat?.....

This time of year approx 24hrs for each coat, but allow 36-48 to be sure at any other time of year.

Hi to all, newbie here - cromboy - got same issue with 1m2 at mother in law's. If I scrape as much bitumen off as poss, can I just seal the floor with a neat coat of BAL bond SBR then lay porcelain using rapidset flexy? Cheers for all the advice given

It is wise to remove as much as possible... then you can mix the sbr with rapidset to create a slurry... 50/50 mix and spread this onto the floor with a paint brush or steel float.. it is called a slurry coat and will aid in the adhesion of the adhesive to the substrate.

Thanks David, will try the slurry method.