How to Paint Cinder Blocks
In their original state, cinder blocks are gray, dull, and lifeless. But it only takes a little color to turn this utilitarian building block around.
Basements, outdoor structures, planters, and exterior walls become vibrant and interesting with a few coats of paint. Interior cinder block projects like bookcases, shelves, tables, and desks take on new life when brightened with paint.
Cinder block's highly porous surface can be a bit tricky to paint. But with the right prep work, you'll be able to paint cinder blocks almost as easy as painting an ordinary wall.
Before You Begin
The key to successfully painting cinder blocks is priming. Primer creates a uniform topcoat that's free of pores. Though optional on other surfaces, primer is required on cinder blocks. Use concrete and masonry bonding primer. Do not use wood or drywall primer or self-priming paint.
After priming, you can use ordinary acrylic-latex paint tinted to the color of your choice. Use interior paint on interior cinder blocks and exterior-grade paint on outdoor surfaces.
For highly moist surfaces like basement cinder blocks, purchase elastomeric paint. This durable, elastic paint works well on cinder blocks and other tough surfaces.
When to Paint Cinder Blocks
Apply primer or paint to cinder blocks only in temperatures between 50 and 90° F. Paint the blocks only when they are perfectly dry.
If you need to use a paint stripper, use it only in well-ventilated areas while wearing eye and breathing protection. Use waterproof gloves. Even natural paint stripper is caustic, so observe the same safety precautions.
What You'll Need
Equipment / Tools
- 1/4-inch or 3/8-inch nap roller
- Nylon or polyester paint brush
- Wire brush
- Nylon brush
- Clean bucket
- Pressure washer (if needed)
- Paint tray and liners
- Paint scraper
- Acrylic-latex paint or elastomeric paint
- Concrete and masonry bonding primer
- Plastic sheeting
- Paint stripper (if needed)
Strip the Old Materials
If the cinder block is coated with failing paint, remove the paint. Paint in good condition can be painted over. Strip off the paint either with a petroleum-based or plant-based organic paint stripper. Caulk, silicone, and any other materials that shed paint should be stripped off with the paint scraper. Use the wire brush to remove paint from the pores of the cement.
Clean the Cement Surface
Unless the cinder blocks are new, they likely need to be cleaned before painting. Since the blocks are so porous, impurities like grease, oil, fingerprints, dirt, dust, and hair cling to and embed in the surface.
- Indoors: Protect the floor with sheet plastic. Mix tri-sodium phosphate (TSP) in a bucket with warm water. Use about 1/2 cup of TSP per 2 gallons of water. Scrub the cinder blocks with a nylon-bristle brush. Rinse with clean water.
- Exteriors: Clean outdoor cinder blocks with a pressure washer. Run a mild detergent through the pressure washer and let it soak on the blocks for about 15 minutes. Rinse the cinder blocks from the top down. Use only a wide spray and stay 3 to 4 feet away from the cinder blocks as they are easily damaged.
Let the Cinder Blocks Dry
Water soaks deeply into cinder block material, so the blocks will need to dry for 24 to 48 hours. It's vital that the blocks be perfectly dry to avoid trapping moisture behind the paint. Cinder blocks that appear dry on the surface may still be wet inside.
Apply Primer to the Cinder Blocks
Small sections of cinder blocks can be hand-painted. For large areas of cinder blocks, use a paint roller. Pour the paint into a lined paint tray. Soak the roller, then roll it out dry on the paint tray. Roll the surface. For mortared joints, follow up with a nylon or polyester brush.
Paint the Cinder Blocks
Let the primer dry for at least four hours or as recommended by the manufacturer. Paint the cinder blocks the same way that you primed them: rolling large areas or hand-painting smaller areas.
If using elastomeric paint for basement walls or other wet surfaces, it's usually recommended that you apply three coats of paint to bring the accumulated paint layers to the desired 10 to 15 mils thickness.
When to Call a Professional
It's best to have a professional power-washer clean outdoor cinder blocks deeply embedded with moss, mold, or mildew. If abating below-grade moisture is the reason for painting the cinder block, call a basement waterproofing company since related issues may also be causing the moisture.