Things You'll Need
Steel mesh sheets
1-by-2-inch wide board
Adding stucco over a concrete block wall is one of the most compatible home projects. It is a simple matter to get the concrete and stucco to bond. However, this bond becomes stronger when a steel mesh is hung onto the wall to create a textured surface to which the stucco can easily adhere. Applying the stucco is a simple process. The complicated part of the job is the cure time that is necessary to prevent cracks.
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Create a barrier of steel mesh over the retaining wall. Screw the metal sheets to the wall with concrete screws and a power screwdriver. It may be necessary to drill a small hole where you want to place the screws first. Place the screws inside the hole for a tight fit. Cover as much of the wall as possible with the steel mesh. This process creates a rough surface that enables the stucco to stick tightly to the wall.
Mix the first batch of stucco in the large bucket. The stucco should have the appearance and texture of thick mud when mixed properly.
Press the stucco into the steel mesh with a notched trowel. Stand on the ladder as needed to reach the higher areas. Spread the stucco to about 3/8-inch thick.
Create a scratching tool by hammering nails about a 1/2 inch apart across a 1-by-2 strip of wood equaling 18 inches in length. Drag the nails across the smooth surface of the stucco to create grooves. This process helps the next coat to stick to the wall firmly and resist flaking, cracking and breaking. Allow the stucco to dry for at least 24 hours.
Moisten the stucco wall with a sponge before applying the next coat of stucco. Mix the second batch of stucco. This "brown coat" makes up the middle layer of stucco between the scratch and top layers. Smooth the stucco over the scratch coat with the large trowel. Apply the stucco about 3/8-inch thick. Allow the coat to cure for 48 hours, damping the wall several times a day with a sponge to prevent cracking.
Apply a thin third layer of stucco over the concrete retaining wall. This coat should be about 1/8-inch thick. After applying, add texture to the wall by dragging a piece of scrap wood across the surface of the wall. Alternatively, you can use the trowel to create circular patterns in the stucco's surface. Allow the wall to dry for 48 additional hours, dampening the wall two or three times a day.
The best weather condition for application is an overcast day with temperatures between 50 and 80 degrees.