How to Prepare a Concrete House for Exterior Paint

Scrape existing paint from concrete exterior walls with a paint scraper and wire brush. Vacuum the paint flakes that fall to the ground with a shop vac if possible. To remove the old paint faster, rent or buy a power washer and follow the accompanying directions for use; at least 2,500 PSI and the use of a 15-degree tip positioned 1 foot away from the wall surface are recommended for walls made of concrete blocks.

Use a solution of trisodium phosphate (TSP) and water (1/2 cup TSP to 2 gallons warm water) with a brush to clean the entire exterior wall surface; rinse it off with clean water. You could also pump the TSP solution through a power washer. Regardless of the method you choose, read the TSP manufacturer's directions first and wear thick rubber gloves.

Allow your concrete exterior walls to dry thoroughly.

Use a trowel and a ready-mix concrete patch to fill and smooth any small cracks, gouges and rough surfaces. Force the patch into the damaged area and smooth it flush to the wall's surface. Allow it to dry thoroughly.

Use a combination primer and sealer to fill and seal the porous surface of your concrete exterior walls. It is thick and should be applied with a roller. Again, allow it to dry completely before applying paint.