Concrete is porous, which means that it readily absorbs liquids like paint. With this ease of penetration, paint can seep millimeters deep into a concrete surface. As a result, it can be a challenge to remove paint from concrete, but it can certainly be done. How long will it take? That depends on the size of the area you’re dealing with. But it’s safe to expect that you won’t be knocking this out before lunch. Think of removing paint from concrete as an ongoing process, not as an item for your weekend to-do list.
MATERIALS AND TOOLS
- Broom (or clean cotton rag)
- Trisodium phosphate (TSP)
- Long-handled brush
- Putty knife
- Chemical paint stripper
- Protective gear
- Pressure washer
- Clay powder or kitty litter (optional)
When you set out to remove paint from concrete, the first thing to do is clean the surface of the concrete thoroughly. Prepare a solution of soap and water, or better yet, diluted trisodium phosphate (TSP)—in which case, be sure to wear gloves. Meanwhile, sweep or wipe off the concrete, removing as much loose dust, dirt, and debris as possible. Now proceed to work the soapy water or TSP into the concrete by means of a long-handled brush. Rinse the area afterward, allowing one to three hours for the surface to dry.
If some of the paint has already begun to chip or peel, scrape it away with a putty knife. Having done so, get ready to apply the chemical paint stripper. You need to use one designed for the type of paint you’re trying to remove. In other words, use oil-based paint stripper on a surface coated by oil-based paint. Not sure which type of paint is on the concrete? If you’re uncertain, your best bet is to opt for an oil-based paint stripper.
Once you’ve covered the concrete with a generous layer of paint stripper, let it sit for six to eight hours. During that time, a chemical reaction will take place, the magical result of which is the removal of paint. Remember that if you’re working with paint stripper, it’s imperative that you wear the appropriate protective gear: a respirator (or at minimum, a dust mask), long sleeves, and good pair of rubber gloves.
For this stage of the job, so long as you’re working on a compact concrete patch, you can probably get by with a wire scrub brush or a paint scraper. On a larger surface, to make things much more manageable, it’s recommended that you rent a pressure washer from your local home center (or borrow one from a neighbor).
Having set the pressure washer at 3,000 psi, go ahead and blast away the paint stripper residue. Soon enough, you will see whether or not it will be necessary to repeat Step 2. It’s not unreasonable to anticipate having to apply and then wash away multiple applications of paint stripper.
What if you spill a gallon of paint on the garage floor, or accidentally leave a thick splatter of bright orange paint on the driveway? To clean it up, you would follow the same basic steps outlined above, with one important exception. Instead of applying a layer of paint stripper alone to the concrete, you would apply a paste made from the stripper and a superabsorbent material, such as finely ground clay powder or pulverized kitty litter.
There are alternatives to using a paint stripper, but they’re all more labor-intensive. For instance, on a concrete surface of modest size, you can opt to use an orbital sander. Likewise, a floor buffer can get the job done on a larger scale. But perhaps the most effective nontoxic option is a soda blaster, a tool very much like a sandblaster, except that instead of sand, it shoots out sodium bicarbonate (baking soda). You can most likely rent one—and buy the baking soda in bulk—at your local home center. Because all of the above options create fine particles, a dust mask or respirator is a must if you’re working indoors.