Painting stucco requires some preparatory steps. Start with a thorough cleaning. Patch existing cracks. Apply primer as necessary.
Stucco is a popular building material used for residential exterior siding. Stucco is a cementitious material that typically consists of sand, Portland cement, lime, and water and in some cases it may contain additional additives.
Cleaning Stucco to Improve Adhesion
A thorough cleaning of all the stucco surfaces is necessary to remove any contaminants that could cause adhesion problems. The following are some of the common types of contaminants:
A pressure washer with the wide angle cleaning tip will generally remove these types of surface contaminants. Additional scrubbing with a medium or stiff bristle scrub brush and a good cleaning solution is recommended for extreme conditions. A scrub brush that can be attached to a telescoping extension pole increases reach and leverage making it easier to work from the ground. Simple Green House & Siding Cleaner is a non-toxic, biodegradable concentrate that works well for exterior surfaces. Laundry detergent, about ¼ cup per gallon of water is also an effective cleaning solution. There are several other available cleaning products that could be used. Try to avoid spraying the high pressure water onto windows and doors.
Hairline cracks are small cracks that usually form during the curing process of new stucco but they can also occur from slight movement due to expansion and contraction. Applying paint coats with a paint roller will typically fill these narrow cracks. The roller action helps to push the paint into the cracks. Paint application with an airless sprayer alone will not effectively address hairline cracks.
Stucco cracks with a width greater than 1/16 inch generally require a stucco patch type filler to bridge the gap. Brush-able elastomeric filler works well for cracks up to a width of 1/8 inch. This type of stucco patch should only be applied to previously primed or painted stucco. Brush the elastomeric filler directly onto the cracks. It is very important to feather the edges of the filler lines with the brush. Failure to do so will allow the filler lines to remain visible after the topcoats of paint have been applied. Inexpensive disposable chip brushes work well for this application.
Thicker grade elastomeric filler can be used to fill stucco cracks greater than 1/8 inch. It is available in cartridges where it can be applied with a caulking gun or standard containers where it can be applied with a flexible putty knife. It is important to feather the edges of the filler lines as is the case with the brush-able elastomeric filler. The thicker stucco patch fillers should also only be applied to previously primed or painted stucco.
Sometimes it is prudent to prime the stucco before applying paint coats. This is a good idea in cases of severe chalking and/or efflorescence, even after a thorough cleaning has been completed. It is also good practice to prime over stucco patch fillers applied to cracks.
Paint burn associated with high alkalinity (pH greater than 11) is another reason to apply a primer coat. This situation is generally found on newer homes that may have been prematurely painted before the stucco had the proper cure time. For this type of condition it is best to use an alkali resistant masonry primer/conditioner.
Repainting stucco can usually be accomplished with one or two coats of paint. Two finish coats are often preferable for a variety of reasons including coverage and paint longevity. The types of paint typically used to paint stucco include the following:
Previously painted stucco can be painted with a brush and roller or an airless sprayer.
Painting stucco with a paint brush and roller does a nice job to fill all the stucco pores and voids found on rougher stucco textures. A 1 to 1-1/2 inch lambskin or lambskin/synthetic combination roller cover is well suited for most stucco textures. A roller frame that can be attached to a telescoping extension pole increases reach and leverage making it easier to work from the ground. A 3 or 3-1/2 inch paint brush with synthetic filaments (bristles) is a good choice for cutting in the paint. A combination nylon/polyester brush works well for this application.
Spray painting stucco with an airless sprayer is an efficient method for large areas where hairline cracks are not an issue. A 517, 617, 515, or 615 spray tip works well for masonry surfaces. Spray painting immediately followed by a paint roller, also known as back rolling is another effective way to paint stucco and address any hairline cracks at the same time. This is more easily accomplished with two people working together. It is important to closely follow with the roller before the paint has a chance to set up. As is the case with spray painting, this method requires all the necessary masking and covering.