How to Stucco Concrete Blocks
- 1). Clean your block walls to remove dirt, oil and grease. A clean concrete wall will be more likely to bond with the stucco and will help ensure a long-lasting application. Rent a pressure washer to clean your wall, working from the bottom of the wall to the top. Unless your wall is very dirty, regular hot water should be sufficient for cleaning.
- 2). Patch any holes or cracks in the blocks. Fill small cracks with a latex concrete caulk, making sure to fill all available space. Use a concrete repair mixture to fill larger cracks or voids. Scrape away excess material to leave the wall surface smooth and level when all repairs are complete. Allow the patched areas to dry for four to six hours before proceeding.
- 3). Paint the wall using a concrete bonding agent and a clean brush or roller. This bonding agent will help the stucco adhere to the block, and will minimize cracks and shrinkage of the stucco over time.
- 4). Choose a pre-mixed stucco blend and add water according to the directions on the package. Properly mixed stucco is fairly thick, and has the consistency of paste or butter. Use a drill with a paddle bit to stir the stucco to ensure it is well blended.
- 5). Apply your base coat. This coat will be 3/8-inch to 1/2-inch thick, and should be applied with a notched trowel. Try to keep the stucco fairly even across the wall surface, but don't worry about appearance or texture on this coat.
- 6). Use a piece of lumber to "float" the wall, removing excess stucco and creating a smooth surface. Once the stucco is just starting to harden, use a stucco rake to create grooves across the entire surface. This is known as a "scratch" coat, and will help the final coat adhere to the wall more securely.
- 7). Allow the first coat to dry overnight, then mix a second batch of stucco and apply your final coat. This final coat should be 1/4-inch thick, and should be textured to create the desired finish. By experimenting with the angle and pressure of your trowel, you can create heavily textured or nearly smooth stucco walls.
- 8). Keep the wall moist. Mist the stucco with a garden hose or spray bottle several times a day for the next three to five days. This will cause the stucco to dry slowly, which can minimize cracking and crumbling.
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