How to Parge a Concrete Block Wall

Parging a concrete block wall is a technique used to coat the surface with a thin layer of mortar to enhance its appearance, protect it from the elements, and improve its durability. Here’s a step-by-step guide on how to parge a concrete block wall:

Materials and Tools Needed

• Portland cement
• Masonry sand
• Water
• Masonry trowel
• Hawk (plasterer’s tool)
• Bucket or mixing container
• Wire brush or stiff bristle brush
• Garden hose or spray bottle
• Bonding agent (optional)
• Protective gear (gloves, safety glasses)

Preparation

1. Clean the Wall:
   • Use a wire brush or stiff bristle brush to clean the wall. Remove any loose debris, dirt, and previous coatings. A clean surface is essential for the mortar to adhere properly.
   • For stubborn dirt, a pressure washer can be used, but ensure the wall is completely dry before proceeding.
2. Wet the Wall:
   • Lightly dampen the wall using a garden hose or spray bottle. This helps to prevent the dry concrete blocks from absorbing moisture from the parging mix too quickly, which can cause it to crack.
3. Apply a Bonding Agent (Optional):
   • For better adhesion, especially on old or smooth surfaces, you can apply a masonry bonding agent according to the manufacturer’s instructions.

Mixing the Mortar

• In a large bucket or mixing container, combine one part Portland cement with two parts masonry sand.
• Add water gradually and mix until you achieve a consistency similar to peanut butter. The mix should be smooth and workable, not too dry or too runny.

Applying the Parging Mix

1. Load the Hawk:
   • Scoop a generous amount of the mortar mix onto the hawk using the trowel.
2. Apply the Mortar:
   • Starting at the top of the wall, apply the mortar with the trowel in a thin, even layer. The typical thickness is about 1/4 to 1/2 inch.
   • Use a sweeping motion with the trowel to spread the mortar, ensuring it fills all joints and crevices.
3. Smooth the Surface:
   • After applying the initial layer, smooth the surface using the trowel. Work from top to bottom and try to keep the surface as even as possible.
   • If you need a second coat for a more even finish, let the first coat dry slightly (until it is firm but still damp) before applying the second coat.

Finishing Touches

1. Texture the Surface (Optional):
   • If you prefer a textured finish, you can use a broom, brush, or sponge to create a desired pattern on the surface before the mortar fully sets.
2. Curing the Parging:
   • Keep the parged wall damp for several days to allow it to cure properly. This can be done by misting the wall with water periodically or covering it with a plastic sheet to retain moisture.

Maintenance Tips

1. Inspect Regularly:
   • Check the wall periodically for any cracks or damages. Promptly repair any issues to maintain the integrity of the parging.
2. Reapply as Needed:
   • Over time, weathering may cause the parging to wear. Reapply a fresh coat as necessary to keep the wall protected and looking good.

By following these steps, you can effectively parge a concrete block wall, enhancing both its appearance and durability.