The three-coat system is the best way for a homeowner to apply stucco to masonry or brick siding. First, the homeowner cleans and preps the wall. Then she applies the bonding agent followed by a basecoat, or scratch coat, of stucco. Finally, she adds the finishing coat to create the rough texture characteristic of stucco. For best results, a homeowner should work on a slightly cool, overcast day to prevent the stucco from cracking due to heat.
To apply stucco to masonry, the homeowner should first clean the wall. This helps the bonding agent stick and set up properly. Cleaning involves washing down the wall and, once the wall dries, applying a bonding agent to it. Taking the project one wall at a time ensures the homeowner won’t need to stop halfway through and run the risk of creating an uneven finish.
After the bonding agent has dried, the next step in applying stucco to masonry is to add the first coat of stucco. This coat is known as the scratch coat because, once applied, the homeowner uses a scratch coat rake to create 1/8 of an inch (3 mm) deep, evenly spaced lines running horizontally along the wall. This is another reason when applying stucco to masonry the homeowner should take the project one wall at a time. If she has to stop in the middle of creating the scratches on the scratch coat, it will be obvious where the lines stop and start again across the wall. The goal is to create one long, continuous set of lines from one edge of the wall to the other.
As the scratch coat dries, the homeowner should mist it occasionally to keep it from drying too fast and cracking. The dry time varies from two to three days. This coat provides a strong, flat surface for the finishing coat of stucco to adhere to.
When the scratch coat is thoroughly dry, it’s time for the homeowner to take the final step. The finishing coat of stucco will create the visible texture on the walls and the homeowner can mix in a pigment to dye the stucco a desired shade of color if she wishes. She should apply this final coat with a flat-surfaced finishing trowel and create the desired texture pattern as she applies the stucco.
Once applied, the homeowner can step back to examine her work and adjust the texture as necessary to create a smoother or more choppy look depending on her preference. The stucco takes another two to three days to dry and needs misting occasionally to slow the drying process and strengthen the stucco. Homeowners with a desire to decorate the stucco can add a special paint designed for use on concrete, but should wait a minimum of six months before painting the house.