How to Apply Stucco to Cement Board
Applying stucco to a cement board can be a time-consuming process that requires patience. It is not as easy as applying stucco to a brick wall, but if you have the right tools and materials beforehand, it can be a joyful process with aesthetically pleasing results.
Step 1 - Measure the Area of the Cement Board
Using a measuring device like a tape measure, measure the area of the cement board you intend on covering with stucco. This measurement will also be required pre-application when you cover the board with mesh.
Step 2 - Trim the Fiberglass Reinforcing Mesh
Get the mesh ready for covering the cement board before applying stucco. It is imperative you do this as without the mesh, the stucco will not hold even after you think it has cured. The bond will be brittle and will come off even with a slight push. Use tin snips to trim the mesh.
Step 3 - Apply Bonding Agent
Once your mesh is ready, the first step is to apply the concrete bonding agent onto the cement board. This will ensure that the bond is doubly strong (combined with the mesh). Using a paintbrush, apply the bonding agent onto the cement board.
Step 4 - Apply the Mesh
After applying the bonding agent, while it is still not completely dry, embed the fiberglass mesh into the cement board.
Step 5 - Apply the Mortar
The first step in applying the stucco is to apply a scratch coat of mortar. Apply a ¼ to ½ inch thick layer using the plastering trowel and hawk. Let it slightly harden.
Step 6 - Scratch the Mortar
After the mortar has slightly hardened, scratch the mortar to a thickness of 1/8 inch and allow the now thinned layer to dry and harden for 48 hours. Using the spray bottle, spray the mortar layer with water during the 48 hours.
Step 7- Apply the Finishing Coat
After the first curing process is complete and the scratch layer is dry, apply another coat of stucco 1/8 to ¼ inch thick using the plastering trowel. This finishing coat can be finished to a texture that you like and should then be allowed to cure for another 48 hours. Keep spraying the cement board with water during this time. Use a putty knife to add detail to the final coat before it dries.
Step 8 - Add Finishing Touches
The most important step after the final layer of stucco is applied is the spraying of water. It is very important to keep the stucco periodically damp for it to cure completely and form a strong bond that will last for decades. After the finishing layer on the cement board has cured, you can add desired texture to the stucco using the plasterer’s rake by scraping in random patterns that you like or a systematic pattern, making the cement board look like a stone wall.