How to ensure a long-lasting coat on stucco
Thursday, July 05, 2007By Bill & Kevin BurnettInman News
Q: I own a stucco home that was built in the late 1940s. It was last painted about 10 years ago and is flaking.
When I lift the flakes off with a putty knife, the underside is white and chalky. The more I lift off, the farther it goes. Although some areas appear tight, some show lifting a day later. There are also some hairline cracks.
What is the best way to prep for painting? Should I rent a pressure washer, and if so, will that remove the chalkiness, or will that take wire brushing? Should the hairline cracks be widened and filled, or will the undercoat provide enough filler? Should the cracks be dealt with before washing? How powerful should the pressure washer be?
Also, I was planning to use Zinsser oil base undercoat, followed by Kelly-Moore Acry Velvet exterior paint.
A: A stucco paint job should last more than 10 years, especially if the paint was of reasonably good quality. We're afraid you've fallen victim to poor preparation.
As we always say, an exterior paint job is only as good as the prep -- and this was a crummy job. The fact the paint is peeling off the chalky surface underneath tells us that the previous "painter" -- and we use the term loosely -- just slapped on a coat of paint to make the place look good. The result is that he wasted a fair amount of time and money and didn't get the longevity he could have gotten with a little more time and effort.
Our compliments to you for doing it right this time. All of the questions you pose are good ones. You're definitely on the right track. Follow these steps to get a long-lasting "Cadillac" paint job.
1. Clean the surface. As far as we're concerned, using a pressure washer is the only way to go. A pressure washer rated at about 1,700 psi will do the job, but if you're renting, go for the larger model. You can always dial it down a bit.
Use a wider spray pattern and go at the wall at about a 45-degree angle so you don't blow a hole in the stucco. Use drop cloths at the base of the wall to catch the paint chips you'll invariably dislodge. We suspect the old paint will come off in sheets.
2. After the surface is dry give any cracks a quick swipe with a wire brush to eliminate any leftover debris. Also check for and remove any paint chips that may have escaped the pressure washer.
3. Prime the surface. The Zinsser product you mention should be OK. Doublecheck to make sure it's suitable for stucco and compatible with the Kelly-Moore finish coat you're planning.
Another option is to use a low-viscosity penetrating sealer. These sealers penetrate any chalking paint that might remain after washing and bond it to the surface. Since you're using a Kelly-Moore finish, take a look at their 98 Stucco Seal. A description and specifications can be found on the Web at www.kellymoore.com.
4. Patch the stucco. For patching hairline cracks, we've had good luck with Bondex Ready-Mixed Stucco Patch by Zinsser. This product has the consistency of a heavy paste, dries to a bright white and cleans up with warm water.
Application is with a putty knife, a broad knife or a heavy paintbrush. Work the material into the cracks and allow it to dry. If there are wide cracks several coats may be required. Because of its thickness this material can be "tooled" to match the existing stucco.
For more information check out the product data sheet at www.zinsser.com.
5. Apply the finish. The hard part's done, now it's time to reap the rewards. Paint your house the color of your choice and rest assured you've done everything you can to ensure a long-lasting job. Hopefully you won't tire of the color. But if you do, the next go-round of preparation will be a whole lot easier.
Copyright 2007 Bill and Kevin Burnett