How to Apply Stucco
by B.E. Conrad
Applying stucco is a great way to enhance the beauty of any home, and the application of this great material is well within the skills of most homeowners. Before the stucco can be applied, consider what type of surface you will be covering. The application methods will vary depending on whether the existing wall is wood, block, brick, concrete or some other type of material.Stucco a Masonry or Concrete Wall
To apply stucco to an existing brick, block or concrete wall, first brush a concrete bonding agent onto the wall, then allow it to dry completely. After the bonding agent has been allowed to dry, the stucco can be applied directly to the wall. The application of the stucco should begin with a scratch coat, a 1/4 to 1/2 inch layer of mortar which is applied directly to the structure and allowed to slightly harden. After the mortar has hardened slightly, it should be scratched to a depth of 1/8" and allowed to harden for between 36 and 48 hours, periodically misting the surface to keep it moist.
After the curing period has passed, a finish coat can be applied. The finish coat will be between 1/8" to 1/4" thick. The finish coat can be finished to the desired texture, then allowed to cure for another 36 to 48 hours, with periodic misting to keep the surface moist.
Stucco a Wood Wall
The procedure for applying stucco to a wooden surface is somewhat different, beginning with nailing 15-pound roofing felt over the structure. After the roofing felt has been installed, it should be covered with 17-gauge metal netting. This netting can be purchased in 150 foot rolls at many home improvement stores. The metal netting is applied by attaching it to the structure using galvanized roofing nails. After the netting is in place the excess can be trimmed using tin snips.
The next step is to apply a scratch coat by using a trowel to spread a 1/4 to 1/2 inch layer of mortar, carefully forcing this mortar into the netting. This will cause the mortar to exude through the netting, which will in turn help to "key" the coating into place.
It is important to complete one wall before starting another one, and to allow the scratch coat to harden slightly before proceeding. After the mortar has slightly hardened, the next step is to use a plasterer's rake or homemade equivalent to scratch the entire mortar coat to a depth of at least 1/8".
When working with mortar, a slow and careful curing will work best and provide the greatest strength. The scratch coat should be allowed to cure for at least 36 to 48 hours before proceeding. During the curing process the wall should be misted periodically to keep the area damp. When the weather is hot and dry, more frequent misting may be required.
After the scratch coat has been allowed to cure, the finish coat can be applied. A flat finishing trowel can be used to apply a finish coat between 1/8" and 1/4" thick to the scratch coat. If a powdered pigment is desired, the pigment should have water added to it and be mixed completely before being added to the stucco. The stucco can then be finished to the desired texture and allowed to cure for several more days.
As the finish coat is curing, it is important to mist it periodically to prevent the surface from drying out. If the stucco is to be painted, wait at least six weeks, and use a paint that is specifically formulated to cover stucco walls.