How to Apply Stucco Mortar

Stucco can lend texture to your walls.

Stucco is a hard mortar covering applied to walls to alter the look of plain block or masonry construction. The stucco material binds instantly to the surface of both interior and exterior walls, and once dried, lasts for decades with only minimal maintenance. As you apply the stucco covering, you can alter the appearance of the material, creating a texture of your choosing.

Things You'll Need

• 3/8-inch wood lath
• Hammer
• Nails
• Concrete bonding agent
• Paint roller or paintbrush
• Portland cement
• Lime
• Fine sand
• Wheelbarrow
• Hoe
• Builder's hawk
• Trowel
• Wooden screed
• Wood float
• Notched trowel
• Stucco finish coat mix
• Spray bottle

Instructions

1. Attach two strips of 3/8-inch wood lath horizontally on the top and bottom of the wall framing the stucco area, using a hammer and nails.

2. Apply a layer of concrete bonding agent onto the surface of the wall between the lath. Use a paint roller or paintbrush to apply the agent evenly. The bonding agent enables the stucco to stick to the masonry surface in a way that allows it to move along with movement in the subsurface. This prevents the stucco from cracking as the surface beneath it expands and contracts with temperature changes. Wait at least 30 minutes for the bonding agent to dry completely.

3. Mix a base coat of stucco consisting of one part Portland cement, one part lime, and four parts fine sand in a wheelbarrow, using a hoe. Add water to the dry mix until the mortar is a stiff but easily-spread consistency.

4. Spread a generous amount of stucco onto a hawk, a flat, table-like handheld surface for transporting the stucco. Use the trowel to scoop the stucco from the hawk and spread it across the surface of the wall with the trowel at a 30-degree angle. Press firmly with the flat of the trowel as you spread the stucco to ensure adherence to the bonding agent. Work from the bottom of the wall to the top, building a coat 3/8 inch thick. Wait five minutes.

5. Place a wooden screed across the two laths. Pull the screed across the surface of the base coat with a sawing motion, leveling it out. Fill in any gouges or dips in the mortar and then repeat the leveling process. The process will leave a moist surface sheen on the mortar.

6. Remove the wood lath pieces, and wait about 15 to 30 minutes for the surface sheen to disappear from the base coat. Drag a wood float across the surface of the mortar, using a swirling motion to prevent shrinkage and cracking in the stucco surface. Use the notches of a notched trowel to scratch the surface of the base coat to a depth of 1/8 inch and allow the coat to cure for 48 hours. Spray the coat with a mist of water to keep it slightly damp during the curing process.

7. Mix a finish coat of mortar for the final layer of stucco. Use a professionally formulated finish coat for consistency across your wall's surface. Mix according to the manufacturer's instructions and then apply to the wall using the same process as your base coat, but to a depth of 1/8 to 1/4 inch.

8. Texture the finish coat according to your tastes. Apply textures with a trowel, broom, stamps, anything that gives you the texture you want. Allow the finish coat to cure for 36 to 48 hours, misting the wall to keep it damp.

Tips & Warnings

• Wear work gloves, safety goggles and a face mask during the application process to protect yourself from hazardous chemicals.

References

• Taylor Rental: Stucco Concrete Block
• Ask The Builder: Applying Stucco

Resources

• Portland Cement Association: Stucco