Concrete absorbs the paint, but while cleaning paint off concrete is difficult, it can be done. It’s easier if the concrete is sealed before painted. If it wasn’t sealed, the paint may have stained the concrete, so even when you remove it, some color may be left behind. Start with the simplest steps and move on to the more advanced ones if needed.
Tip: Whenever you’re removing old paint, lead-based paint may be a concern. If the paint was laid down before the late 1970s, it’s likely there’s lead in it. This is dangerous. Consult a professional before proceeding.
Clean the floor thoroughly before you begin the process of removing paint. This will help ensure that nothing on the floor can cause problems with any paint removal chemicals you may use. Use soap and water and a scrub brush to scrub any stains or locations where there might be oil. Trisodium phosphate, or TSP, is ideal for this type of cleaning. Ammonia is also good at cutting grease and oil. For stubborn stains, try using a wide wire brush after some of the oil is removed.
Step 2: Use a Pressure Washer
Using a pressure washer is a good first step to removing paint. Pressure washers often have enough power to remove paint. This is especially true if a sealant was used on the concrete prior to applying the paint. You will need a pressure washer capable of putting out 3000 psi. There are different spray tips for pressure washers and there is one specifically used for stripping paint while others are for just washing off dirt and mold. Make sure to use the proper tip.
Step 3: Use a Power Sander
If a pressure washer does not work you can attempt using a sander. Be careful with the sander because it can damage concrete. Protect yourself as well. Wear long pants and a long-sleeve shirt along with a face mask and protective goggles. Use coarse to medium grit sandpaper and run the sander over the surface. Don’t concentrate too long on a single area, or you can create a low spot in the concrete.
Step 4: Use a Chemical Removal
There are a number of chemicals designed specifically for the purpose of removing paint from concrete. The biggest factor which determines how well this method works is whether the paint has sunken into the concrete. If it has not, this method will work quite well. Follow the directions on the container for how much to use and how to use it. Also, make sure that the room you are working in has plenty of ventilation. However, even with good ventilation, a good respirator is essential for safety. Apply the chemical to the areas with paint and allow them to sit for a while before cleaning up with a mop.
Once all the paint is removed and the floor is cleaned, etching with muriatic acid is recommended when using an epoxy finish coat. Special respiration and ventilation steps are necessary and might be undertaken only by the very advanced DIYer.
Step 5: Rubbing Stones
Using rubbing stones is an option for more ingrained paint if it is in a relatively small area. Wear gloves to protect your skin, and use the rubbing stone in a circular motion until the paint begins to come up from the concrete. Make sure you keep firm pressure on the rubbing stone during use. Just like with the sander, don’t rub too much in the same spot to avoid damaging the concrete.
Concrete’s porous nature makes this a tough job, but some elbow grease, determination, and knowledge can get it done.
Edward Kimble, a professional painter and the author of Interior House Painting Blog, contributed to this article.