Removing roofing tar from concrete takes a combination of scraping, chemical softening, and stain treatment. The tar itself is a thick, petroleum-based material that bonds stubbornly to concrete’s porous surface, so a single method rarely does the job. Plan on working in stages: remove the bulk material first, dissolve what remains with a solvent, then treat any residual staining.
Scrape Off the Bulk Material First
Before reaching for any chemicals, get as much solid tar off the surface as you can. A plastic scraper works well here and won’t gouge or scratch the concrete the way a metal blade might. If the tar is thick, a putty knife or floor scraper with a stiff blade can handle the heavy lifting, but switch to plastic for the final passes near the concrete surface.
Cold tar is brittle and easier to chip away. If you’re working in warm weather, the tar will be soft and gummy, making it harder to scrape cleanly. Try working in the morning before the sun heats the surface, or lay a bag of ice over small patches for 15 to 20 minutes to firm them up. Once the tar is brittle, it pops off in chunks instead of smearing.
For large areas, a power washer at 3,000 PSI or higher can blast away loosened pieces, but pressure alone won’t dissolve tar that has soaked into the pores of the concrete. Scraping is really about reducing the volume of tar so your solvent doesn’t have to work as hard in the next step.
Dissolve Remaining Tar With a Solvent
Once you’ve scraped away the bulk, you’ll still have a thin, sticky layer clinging to the concrete. This is where a chemical solvent does the real work. You have several options depending on what’s available and how much tar you’re dealing with.
Citrus or Soy-Based Removers
Biodegradable solvents made from citrus or soy oils are effective and produce fewer harsh fumes than petroleum-based products. These are specifically formulated to break down asphalt, roofing tar, oil, and grease on concrete, stone, brick, and other masonry. You apply them by pouring, spraying, or brushing the product directly onto the tar in concentrated form, then let it sit until the tar begins to dissolve. Contact time varies with the thickness of the residue, but these products have a low evaporation rate and can keep working for up to 24 hours. That long dwell time makes them a good choice for heavy deposits you can treat overnight.
Mineral Spirits, Paint Thinner, or Turpentine
These petroleum-based solvents break down tar effectively and are easy to find at any hardware store. Pour or brush a generous amount onto the stained area, let it sit for 10 to 15 minutes, then scrub with a stiff-bristled brush. You may need to repeat this several times. These solvents evaporate faster than citrus-based products, so reapply as needed to keep the surface wet while you work.
Kerosene or Diesel
Diesel fuel is one of the most commonly used solvents for breaking down asphalt and tar in professional settings. It works, but it leaves its own oily residue behind and carries a strong odor. Use it only in well-ventilated outdoor areas, and be prepared to degrease the concrete afterward.
Whichever solvent you choose, apply it, let it penetrate, then scrub with a stiff broom or brush and rinse with a pressure washer or strong hose stream. For stubborn areas, repeat the cycle: apply, dwell, scrub, rinse.
Treating Deep Stains and Oily Residue
Even after the tar itself is gone, you’ll often see a dark, oily shadow where it sat. Concrete is porous, and the oils in roofing tar seep below the surface. Getting those out requires pulling the oil back up through the concrete rather than just cleaning the top.
A simple poultice does this well. Mix an absorbent powder (cooking flour, baking soda, or powdered laundry detergent like Tide) with paint thinner or turpentine until you get a thick paste. Spread it over the stain about a quarter-inch thick and cover it with plastic wrap to slow evaporation. Leave it for 12 to 24 hours. The solvent breaks down the oil trapped in the pores, and as it wicks upward, the powder absorbs it. Sweep up the dried poultice and repeat if the stain is still visible.
An alternative two-step approach skips the paste. First, apply paint thinner or turpentine directly to the stain and let it soak in for several minutes. Then spread a thick layer of powdered laundry detergent over the wet area. The detergent’s chemical properties attract oil, so as the dissolved tar wicks to the surface, the powder captures it. Leave it overnight, sweep it up, and rinse. This method works because the detergent is specifically designed to bond with oil molecules, making it more effective than plain absorbent powders.
For any remaining shadows, a hydrocarbon-based degreaser scrubbed in with a stiff broom and hot water can pull out the last traces. Heat helps, so working on a warm day or using hot water accelerates the process.
Protecting Yourself During the Job
The solvents that dissolve tar are not gentle on skin or lungs. Chemical-resistant gloves are essential. Nitrile gloves are a reliable choice for most solvents used in tar removal, but check the product label, since different chemicals require different glove materials. Neoprene and butyl rubber gloves offer broader chemical resistance if you’re using multiple products.
Work outdoors or in a space with strong airflow. Petroleum-based solvents like mineral spirits, paint thinner, and kerosene all produce fumes that cause headaches, dizziness, and irritation with prolonged exposure. If you’re working in a garage or partially enclosed area, set up a fan to move air across the work zone. Safety glasses protect against splashes, and old clothes you can throw away afterward are better than trying to wash solvent-soaked fabric.
Containing Runoff and Waste
Chemical-laden water running off your driveway or garage floor can reach storm drains, which typically discharge untreated into rivers, lakes, or other surface water. Solvent runoff can also soak through soil and contaminate groundwater.
For small jobs, absorb the used solvent and loosened tar with cat litter, sawdust, or rags, then bag it for disposal. Check with your local waste management service about hazardous waste drop-off, since most petroleum solvents can’t go in regular trash. For larger jobs where you’re rinsing with water, block nearby storm drains with sandbags or berms and collect the runoff in a bucket or lined pit. Keep your work area at least 50 feet from storm drains, ditches, or any open water.
Citrus and soy-based solvents are biodegradable, which makes disposal simpler, but “biodegradable” doesn’t mean harmless in concentrated form. Contain and dispose of all waste responsibly regardless of the product type.
Choosing Your Approach by Job Size
- Small drips or footprints: Ice the tar to harden it, scrape with a plastic scraper, then spot-treat with mineral spirits and a stiff brush. Follow with a poultice if staining remains.
- Moderate spills (a few square feet): Scrape the bulk, apply a citrus or soy-based remover and let it dwell for several hours, scrub, pressure wash, then treat residual stains with the detergent method.
- Large areas or thick deposits: Use a floor scraper for bulk removal, apply a commercial tar remover rated for masonry in concentrated form, allow up to 24 hours of contact time, pressure wash at 3,000+ PSI, and plan on two or three rounds of stain treatment for the remaining discoloration.
Patience matters more than force with this job. Tar that has been on concrete for months or years will have penetrated deeper into the pores, and no single application of any product will pull it all out. Each round of solvent and scrubbing draws more oil to the surface. Two or three treatments over a couple of days will get results that one aggressive session won’t.