Ask the Builder

Removing Foundation Tar

By Tim Carter
©1993-2008 Tim Carter

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Summary: Removing foundation tar is not easy. It can also be dangerous. Do not use solvents like gasoline, paint thinner or mineral spirits because of the extreme fire danger.

Dear Tim: I am putting in a new patio at my home and had to dig out quite a bit of dirt from around my foundation. Now I have the tar that they used to seal my foundation exposed. What is the easiest and best way to remove the tar so I can paint the foundation that is now exposed? I was told by someone in the store that I would have to peel it off but, that would take forever since it is a pretty large area that needs to be done. Is there a chemical that I can use to remove it? Kim P.

Dear Kim: That dampproofing tar is probably old-fashioned asphalt cement. If so, the only liquids I know that will get it off are volatile and dangerous solvents like paint thinner, gasoline, kerosene, etc. These are all distilled hydrocarbons that can soften the tar. I would not use them as the fire hazard is so extreme.

The first thing I would try is a sandblaster. If you are lucky, a tool rental shop may have a small sandblasting kit that works off of an air compressor used by carpenters. Test it for effectiveness. If it works, then move up to the industrial sandblaster that uses the giant compressor contractors use to power jack hammers.

If this fails, then contact the different foundation dampproofing companies in your area. Tell them you have to remove asphalt cement from a foundation and see if they have a suggestion. After all, they apply the asphalt cement all day and perhaps they make mistakes and spray it where it doesn't belong.

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