What Is a Base for Stucco?

Non-wood Stucco Base

• Stucco applied to solid substrates such as concrete block walls, poured concrete, old stucco, stone or brick needs a 3/8-inch base or scratch coat made of the same materials as the top coat of stucco. It must dry completely before applying the top coat to ensure the two layers tightly bond. For best results, leave the finish of the base coat smooth and free of designs or texturing.

Wood Stucco Base

• Applying stucco over wood requires more steps to create the base. Cover the wood with building paper, and secure the paper with a base strip attached with galvanized nails. Use the same type nails to attach sheets of steel mesh to the area above the base strip. Prepare the same stucco mixture used on masonry, and use a notched trowel to spread the stucco, making sure to get the mixture into all the holes of the mesh to create an even surface and hide the mesh. Let the base coat dry before applying the top coat.

Structural and Design Considerations

• Before beginning a stucco project, carefully examine the walls for any signs of water or excessive dampness, which significantly compromises the integrity of stucco. Pay close attention to flashings around windows and doors, and correct any water seepage issues before applying the base coat. Stucco is an excellent mask for imperfections and irregularities in surfaces created by metal or wood studs. It also hides mortar joints in brick, stone and concrete block walls. If you prefer colored stucco, add pigmentation to the top coat a little at a time to control the brightness of the hues. Use finishing tools to create textures and decorative patterns in the top coat of stucco while it is still wet.

Tips and Hints

• The best climate for stucco application has low wind and moderate temperatures between 50 and 60 degrees Fahrenheit. Hot weather can dry the stucco too quickly and cause cracks and shrinkage. Cold weather tightens the stucco mixture and makes it difficult to spread. For best adhesion, mist brick, concrete blocks or poured cement walls with cool water prior to applying the stucco base.