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Exterior Paint Preparation
By Winston Montgomery
Good writing is said to be 5 percent inspiration and 95 percent perspiration. You could say that another venerable craft painting is 5 percent decoration and 95 percent preparation. Careful prep is the foundation of any good paint job, and it usually explains the vast difference between bids given by experienced professional painters and seasonal student-staffed painting crews. Good preparation creates a clean, sound and smooth surface for optimum adhesion. So if you want your new paint job to look good and last a long time, follow these five steps of surface prep. |
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Planning to Paint
If you're painting your own house, you actually have a few advantages over a professional painting crew. You don't have to rush to get the job done, for one thing. And instead of tackling the entire house all at once, as a professional crew would, you have the option of concentrating on just one section the most weather-beaten side, for example. Cutting a big job down to size can help you fend off discouragement.
Make sure to get the right gear for paint prep. The tools mentioned in this article will help make hard work go easier. Painters' drop cloths, for example, are designed to suck up spills, and they provide far better footing than plastic or old bed sheets.
Safety: Some house paints used before 1978 contain lead. Scraping, sanding and power washing such paints can be hazardous. If you have an older house, check with local building or health officials to see if the paint on it should be tested for lead before you do any prep work. |
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Step by Step
1. Put down protection and tie back plants. Use fabric drop cloths to cover driveways, walks, lawns and decks beneath your work.
Prune and tie back shrubbery next to the house. Use plastic drop cloths to cover any plants that might be damaged by cleaning solutions or paint. Don't leave plants tightly wrapped in plastic for many days or they will suffocate.
The runoff from washing the house, as well as fumes from the drying paint, could harm some plants. If you have delicate or very special plants near the house, you might consider moving them or hiring a gardening expert to move them into containers for the duration. |
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2. Wash the house. Most professional painters begin their exterior prep by washing the entire house with a pressure washer, and you can do this too, with rented equipment. Power washing blasts away dirt, grease, mildew and loose paint; it can even eliminate the need for hand scraping. You can add a house-wash detergent and bleach to the power washer, but the force of water alone is usually enough.
Don't power wash if you have old or weathered wood siding with cracks or gaps in it. The high-pressure water may get into your walls. Instead, scrub down the areas you're going to paint with a solution of TSP and water. Use a scrub brush or an abrasive sponge; add household bleach (about one quart per gallon of water) to get rid of mildew. After washing, rinse with a garden hose. |
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3. Scrape and sand. Now the chips are going to fly. This is the messiest and most strenuous part of paint prep. Wear cotton gloves and a good dust mask or respirator. Protect your eyes with goggles. And stock the refrigerator with Gatorade.
Make sure the wood has dried out before you scrape off any loose, peeling or blistered paint. The best scrapers have long, comfortable handles and take replaceable carbide blades, which stay sharp far longer than steel. You'll need at least two: a wide one, about 3 inches across, and a narrower one for detail work. |
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Scrape firmly, but don't gouge the wood underneath. Remove the paint that's loose, not the stuff that's adhering firmly. If you're dealing with large areas of loosened paint or thick cracked deposits that don't respond to scraping, consider using a special disk sander designed for paint removal. Rental agencies usually carry these, along with a supply of replaceable sanding disks. Alternatively, you can remove problem paint with a heat gun or chemical paint stripper. |
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After scraping, use coarse (50- to 80-grit) sandpaper to smooth uneven surfaces, and feather the edges of chipped paint gently down to the adjacent wood. Lightly sand the entire exterior to etch any residual gloss and remove dirt, chalky deposits anything that can keep the new paint from bonding well. A random-orbit sander is a blessing for this job. Sand molding, interior corners and other hard-to-reach areas by hand. Painted masonry surfaces like brick, concrete, stone and stucco can be cleaned with a long-handled wire brush. |
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As you work around the house, fasten loose trim with hot-dipped galvanized nails or screws, and use a nailset to push old nail heads below the surface. Replace any decayed or damaged trim. Small areas of rotted wood may be stabilized with a penetrating epoxy wood rebuilder that seals out moisture and oxygen while solidifying the wood fibers. Check for loose or missing putty on window sashes, and repair these spots with glazing compound. (You may want to check out our article on how to repair a broken window.)
4. Spot-prime. Existing paint that's sound and clean won't require a primer coat. But bare wood and heavily scraped areas must get a coat of primer. Most pros also prime spots that need applications of filler and caulk because these materials adhere better to primer than to raw wood or old paint. Also, prime any areas of flat paint that will be top-coated with a glossy finish. Be sure the primer is compatible with the materials you're covering. Masonry and rusted metal will require a different primer than the one you use on wood, siding or stucco. The best treatment we've used for rusted metal is rust converter, a milky-white liquid that dries clear and chemically neutralizes the rust. |
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5. Patch and caulk. To fill nail heads, holes or small craters, use a vinyl-based exterior patching compound. These fillers tend to shrink, so you may need more than one application. Alternatively, you can slightly overfill depressions, then sand them flush with the surrounding surface when they're dry.
If you have large, deep areas to fill, like big cracks in wooden windowsills or missing chunks of trim, patch these with a two-part epoxy wood filler. Make sure to spot-prime those areas before you apply the topcoat. Use an exterior grade siliconized latex or tripolymer caulk (also called exterior painter's caulk) to fill open joints, cracks and gaps between molding and siding. |
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Tip from the pros: Never use pure silicone caulk it won't bond with paint.
Shoot the caulk generously into the seam, then push it in and tool it smooth with your index finger. Some caulks shrink, and you may need two applications in wider spots. If the gap you are filling is bigger than 3/8 inch, stuff in foam backer rod (sometimes called foam tape) before you apply caulk; you won't need to use so much. Keep a small pail of water and a wet rag with you to clean your finger.
If you've gotten this far, it's time to take a breather. The most difficult and time-consuming part of your house-painting project is finished, and you haven't even opened your first gallon of paint. You can rest easy, though, knowing you've prepared the way for a job that a professional painter would boast about.
Winston Montgomery has been a painting and drywall contractor in the San Francisco Bay Area for over 25 years.
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