How to Paint Cinder Blocks

Cleaning the Cinder Blocks

Remove powder deposits with masonry cleaner. Some cinder blocks that have been exposed to water through a leak will develop a white powder coating on the outside. It can be removed by scrubbing the deposits with cleaner and a scrub brush. Allow the cleaned areas to dry completely before washing the walls further. Alternatively, you can mix the masonry cleaner with water in a 1-to-1 mixture in a pressure washer and clean the surface of the cinder blocks with the pressurized mixture. To avoid future deposits after painting, locate the cause of the leak and repair it appropriately before priming and painting.

Use a putty knife or paint scraper to remove any current paint. Cinder blocks are mostly all a shade of gray or taupe, so if your blocks are another color or have a shine to them, they’re probably painted. Lift off the paint with the edge of the scraper. Chip away small portions at a time until as much of the paint is removed as possible. Don’t worry about very small pieces that are still present after you remove most of the paint. You can normally scrub these off with water or paint over them without any problem.

Wash the blocks with a pressure washer or hose and scrub brush. Using a pressure washer on a mild pressure level of 1500-2000 psi will get the job done quickly, but it’s okay if you don’t have access to one. You can use a regular garden hose to spray down the blocks and then scrub with a brush to remove dirt. Avoid using soap in the water because it will take longer to dry and isn’t effective for cleaning bare cinder block.

Allow the blocks to dry for 48 hours after getting wet. The primer won’t stick if it’s applied to wet cinder blocks. If you’re working inside, open windows or turn on fans to allow the cinder blocks to dry out quickly. Be patient. If all of the blocks aren’t dry after 48 hours, you should wait a couple more hours before priming.

Seal cracks with polyurethane caulk. Purchase a tube of caulk at the hardware or home improvement store and locate any cracks in the cinder block. Cut about 0.25 inches (0.64 cm) off the tip of the caulk and push the caulk to the tip of the tube with your hands or a caulking gun. Then, apply the caulk to the crack liberally, covering the joint completely. For a smooth finish, run a razor over the applied caulk to flatten the joint and make it blend with the rest of the block. You can also use this method to seal cracks between individual cinder blocks and protect against water leakage.

Priming

Select a bonding and filling primer. At the hardware or home improvement store, look for primers that are latex acrylic-based. These will work best for most cinder blocks and will fill in any cracks and pores in the blocks and neutralize the pH while you’re painting. If you’re painting an area that has a water leakage issue, such as a basement, or painting blocks that are located outdoors, look for a waterproof primer. Bonding and filling primer will work for both smooth and split-face cinder blocks. Make sure you measure the height and length of each wall, and add the areas of each wall to find the total that you’ll be painting before you go to the store. Then, ask the sales associate for a recommendation on the amount of paint you should purchase based on the area.

Apply a coat of primer using nap rollers. Use long, even strokes when applying the primer. Depending on the roughness of the blocks you’re painting, use a 0.5 in (1.3 cm) nap roller for rough surfaces or 0.25 in (0.64 cm) nap roller for smooth surfaces. One coat of primer will be plenty if you’re painting over with a different color. If you’re only priming the blocks, a second coat will ensure the paint sticks and prevent wear over time.

Allow the primer to dry for 24 hours before painting. It’s important that the primer is completely dry before you begin to apply the next coat. Check on the blocks after 24 hours. They should be completely dry to the touch with no transfer onto a finger or glove.

Painting

Purchase high-quality acrylic latex paint. Cinder blocks require a durable paint to hold up to wear and tear. Latex paint with acrylic will provide the best coverage and the smoothest application for both smooth and split-face cinder blocks. To determine how much paint to buy, use the same area measurements that you used to purchase the primer. Ask a store associate how much paint they recommend for the area, which will vary based on the brand. At the hardware store, purchase a half-gallon of extra paint in case you need to touch up the paint in the future. If the paint will be on exterior blocks, select a paint that is also weatherproof to prevent damage from the elements.

Apply an even coat of paint using a 0.5 in (1.3 cm) nap roller. It’s important to work slowly and with a little bit of paint at a time to ensure an even application and prevent dripping, which will be visible on the cinder blocks. Work vertical sections, covering as much as possible with long strokes of the roller. Try to avoid overlapping sections, as these will take longer to dry and can give an uneven look to the first coat. If you have smaller areas that need to be painted, use a nylon polyester brush.

Allow the first coat to dry for 12 hours. Keep the room well ventilated with fans if you’re working indoors, and check on the paint after 12 hours to ensure that it’s completely dry. Do this by touching the paint gently with a rag or gloved finger. There should be no transfer. If you live in an area that’s more humid, you might need to wait up to 18 hours before the paint dries.

Apply a second coat of paint using a 0.5 in (1.3 cm) nap roller. Like the first coat, you’ll want this to be as even as possible. Work slowly, taking a little bit of paint on the roller at a time and applying in long, smooth strokes. For hard to reach or tight places, you can use a brush, but your brush strokes may be visible on smooth cinder blocks.

Allow the paint to dry for 24 hours. Keep the room area ventilated with fans if you’re working indoors. Test to see if the paint is dry by touching it with a gloved hand or rag in an inconspicuous area. There should be no transfer. If the second coat isn’t even or you want better coverage, you can apply a third coat to the blocks. Be sure to wait at least 12 hours before applying a third coat.