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Roofing tar on concrete floor - tiling over tar

We purchased a house that had a subfloor placed over a concrete slab. The previous owner had placed 2x4s flat on top of roofing tar and nailed 3/4" plywood on top of that for flooring. I want to remove the subfloor and install tile over the concrete. We have to heat the tar to take off as much as we can, it is very thick and uneven. Can we use thin set on top of the remaining tar? It is impossible to remove all of the tar, it is smeared across the entire slab.

Re: Roofing tar on concrete floor - tiling over tar

Have you tried to sc**** away the tar? I know this can be back breaking work but is the optimal choice. After scraping, a scarifying process will most likely be needed. Do NOT use any type of solvent or heat as that will get the petroleum distillates deeper into the slab and cause adhesion problems.

Do you have the height to have a drypack or "mud" floor poured over the top of the tar? The mudpack would need to be no thinner than 1" at its thinnest point.

Re: Roofing tar on concrete floor - tiling over tar

I have used a product called "Kroil". It is an oil based penetrating oil unlike W-40 which is a water based lubricant. I have cleaned many many tools covered in tar and oil while working construction. This may be a special order at a specialty Auto parts store. I have never seen it at an Advanced or Auto-Zone. I would also be leary of the adheasions after you use this, but if you pour it over the floor and use a very stiff scrub brush you will get it manageable after some laborous work.

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