Stucco & Some Questions Asked
Can stucco, portland cement plaster, be cleaned, and if so, what methods should be used?
Whether you have some type of atmospheric contamination, biological growth, or staining from another construction process, stucco can be cleaned effectively. Because it is important to choose an appropriate cleaning method based on what actually created the stain, there is no single best process for cleaning stucco surfaces. To clean a dirt-contaminated surface, the following advice is useful.
Like concrete and masonry, stucco is porous. Cleaning methods are similar. It is recommended to wet the substrate starting from the bottom and working toward the top. Prewetting the surface helps the wall shed water, preventing dirty water from being drawn into dry pores. It also begins to loosen soil so that it can be rinsed away. A garden hose may be effective. Special fan-type sprayers are available for increased cleaning power. Whenever using water on a cement-based material like stucco, the substrate should have set and hardened. Water under pressure can etch the surface and at higher pressures can even cut through hardened stucco. To prevent this, the water spray should be moved over the surface uniformly.
Most dirt is removed fairly easily. Cleaning power is increased by doing one or more of the following: increasing water temperature, scrubbing with a brush, or using some type of chemical detergent.
To clean stains other than simple soiled surfaces refer to the reference documents for additional recommendations. You always should test the method on an inconspicuous area to first demonstrate its effectiveness and to assure that it won’t damage the plaster.
Can stucco (portland cement plaster) be applied directly over painted brick?
This is a common question that often arises when people are rehabbing or updating older construction. Plaster is a cost effective finish, relatively easily installed, that improves the appearance and creates a water resistant wall surface.
A painted surface will not typically absorb water and, as such, is a substrate to which stucco will not readily bond—at least not uniformly. There are two basic alternatives to covering a painted brick surface with a new coating of portland cement plaster.
Sand blast or water blast to remove the paint in its entirety, then direct apply a two coat system. It is essential to have a surface that is uniformly absorptive to accept the plaster coating. In addition, it may be beneficial to use a bonding agent or dash bond coat with this approach.
Attach paper backed lath or install appropriate building paper between wall and attached metal lath to provide a moisture barrier and to serve as a bond breaker. Apply traditional three coat stucco to metal lath and accessories. In this approach, the idea is to treat the plaster like a sheathed system, using metal lath to support the plaster on the substrate, while completely isolating the plaster layer from the backup with building paper. This prevents a partial bonding situation, which could set up undesirable stresses in the plaster and lead to cracking.
Can I paint stucco to get the color I want?
Stucco can be painted. Portland cement-based paints are very compatible with stucco because they are made of the same material. These paints should be scrubbed into the surface and fully cured. Alternatively, you could consider a colored stucco finish. These finish coats are often made with white cement and pigments, providing the widest range of colors. Premixed materials are color matched from batch to batch and are most consistent.
Additionally, the fact that you are placing a finish coat with a nominal thickness of 1/8 inch instead of a paint layer usually gives more assurance of complete coverage. It is possible to paint with other types of paint, though these are usually not as long lasting as cement-based paint. Acrylic paints are long lasting and durable but change the permeability of the stucco (make it non-breathable) which in some climates may have adverse effects on the long-term performance of the system.
Stucco being one of the oldest applications used on buildings in our time. If you have anymore questions need be asked, please check out our website by clicking here.