Q:My stucco house has never been painted, and from years of never being cleaned it is very dirty. I have had several power-wash companies look at the house. They have tried various chemicals and they do not seem to take this dirt or mold off. None of the companies has washed the house, they have only looked at it and then refused the job.
A: Your house needs more than just a good cleaning. It needs the finish refurbished. We don't doubt that your house has never been painted. But we do question that it never had what is known in the plastering trade as a "color coat."
Stucco is a porous material made of water, lime and cement. If left unsealed, over many years it will become stained. That is the condition we think you face now.
Your question brings back memories from our youth. We've written before that our dad was a master plasterer. He could do anything with the mud, from the finest ornate ceiling work in San Francisco to coating a tract home in Newark. After working Monday through Friday on his real job, he and his buddy, Babe Mesquite, would take on "little jobs" on Saturdays to earn a few extra bucks. Many of these side jobs would be to redo the color coat on tract homes in San Leandro or San Lorenzo.
As we see it, you've got two choices to spruce up your home: a new color coat or paint.
Plastering should be left to the pros. Contact two or three licensed, bonded and insured plastering contractors for quotes.
Painting you can do yourself. The first step is to clean the surface. The quickest and easiest way is with a pressure washer. The water blasts away dirt (not stains). Pressure washers can be a little tricky to operate. For unpainted stucco adjust the spray pattern to a wide spray. Start on an out-of-the-way part of the building to get the hang of using it. Pull the trigger (there will be quite a kickback) and move the wand over the wall in a consistent side-to-side pattern. An additive designed to kill mildew is available to use with the pressure washer. Use it.
Pressure washers are available at rental centers. Make sure to ask the salesperson for a quick tutorial on operating the machine.
Once the building is washed, let it dry for a few days. Wood trim can take as long as a week to dry, depending on the weather. While the building is drying out, scrape off any residual loose paint. Feather the edges of scraped areas with 120-grit sandpaper. Carry a dust brush with you to brush any sanding dust off the newly washed building.
Next, apply a high-quality, stain-blocking latex or oil-based primer, which is a critical step when working with unpainted stucco. The primer will seal the stucco, preventing the finish coat from being absorbed unevenly and looking splotchy. Add a mildewcide to the paint to protect against the rebirth of fungus that may have been present.
We suggest you buy the paint at a store that caters to the trade. The salespeople will be able to suggest primer that is compatible with the finish you select. They also are a fount of useful information should you ask - and you should.
Allow the primer to cure according to the manufacturer's instructions before applying the finish coat. While the primer is curing, caulk any open joints or cracks in the stucco with a good-quality acrylic caulk. Smooth the caulk with a wet rag. Don't think about leaving the primer unpainted. Primer is designed to act as a base for the finish. If left unpainted for any length of time, it will fail, and all of the preparation done to this point will have to be redone.
The final and most exciting step is the finish coat - "putting on the color." Use a top-of-the-line, 100 percent acrylic house paint in the sheen of your choice - flat, satin, semi-gloss or gloss. The shinier the finish, the more any defects will show. We've always been partial to a satin sheen for its washability and because it hides defects well. Because you are dealing with a previously unpainted surface, the stucco may require two coats of the finish.
Over the years, we've used brushes, rollers and airless sprayers to apply primers and finishes. Our best results have come from using the airless sprayer to apply paint to large surfaces, then going back over the area with a roller or a brush while the paint is still wet. We think that method gives us the best of all worlds. The sprayer gets the material on quickly, and the brush or roller gives a uniform coat that gets into all the nooks and crannies.