If you own a home whose stucco finish siding has been painted, there will probably come a point when you want to repaint, and have to remove the existing paint entirely. Previous owners may even have applied multiple layers of different colored paint, and when these start to peel, it can make repainting even more difficult. You might be wondering what you can do to get the new coat of paint to best adhere to the stucco. Obviously all existing paint should be stripped off.
What not to Do: Don’t paint over the existing paint. This might seem a temptingly easy short-term solution, especially if you are trying to sell your house quickly, but your new paint coat will not last long, and will likely not even look that good.
Do not use sandblasting or chemical methods. Sandblasting is dangerous, since it can remove more of the thin underlying layer of stucco than you want, damaging your siding. Chemical treatments are not recommended, for the same reason, being too hard to control.
To remove old paint on stucco cement, get a high pressure sprayer. Water blasting is quick and clean, and much easier to do than sand-blasting. You can rent one from a tool rental dealer or large paint store. The sprayer needs to be able to develop around 1500 p.s.i.
You need to get one with adjustable pressure settings; that way you can maintain water pressure at an optimal level, not to weak, but still safe enough not to damage your stucco. You need to take great care not to damage the stucco, since even small cracks can permit moisture infiltration, leading to delamination of the stucco from the underlying structure during freeze/thaw cycles.
Following the water-blasting of the old paint, you must check all surfaces for damage and any remaining paint. Hand scrape as required to remove all peeling paint.
The next step is to prepare the bare stucco for the paint. You will need to let your surfaces dry for at least 48 hours after water-blasting. To prep the stucco for maximum adhesion, the best method is to add a product called E-B Emulsa-Bond to the first coat of paint.
E-B Emulsa-Bond is a stir-in bonding primer manufactured by Flood Co. In addition to making the paint adhere better to chalky, porous surfaces, it also lubricates the paint, making it go on smoother, without as many brush marks.
Your paint should be a premium grade Acrylic Latex. The Emulsa-Bond can will have directions on how to mix the paint and bonding primer. Use the 50/50 ratio mix: 1 ga. Of Emulsa-Bond, to each 1 gal. of your paint. By the way, to clean your brushes after using the Emulsa-Bond, first wash away as much as possible with water, then rinse them with paint thinner and one more wash with water. I got that tip from a professional painter.
Allow 48 hours for the bonding primer coat to dry, then apply the finish coat, using just the latex paint you used in the mixture (without the water and Emulsa-Bond).
Stucco is a rather porous material, so you should plan on 1 gal. of acrylic latex paint for every 300 square feet of surface to be covered, not the 400 square feet it says on the paint can.
Photo by Angie Harms, Creative Commons Attribution License