Most people think of painting as a way to make a house look pretty, but it also protects the exterior from the elements. When you're painting the exterior of a house yourself, follow two simple rules: prepare the surface well and buy the best paint you can afford.
First, do a quick test to determine the extent of the work. Choose an inconspicuous place where paint is at its worst. Clean the surface, let it dry and paint a small patch. The next day, press on a piece of tape and then quickly pull it off. If the tape is clean, it's safe to repaint after washing and prepping the whole house. If the tape pulls off all the paint down to bare wood, the house needs to be stripped before it's repainted.
Most old houses are covered with oil paint. When the time comes to paint the exterior of your house with a new coat, you have two options: touching-up or stripping bare. You can try periodic touch-ups with oil but the paint will continue to peel as it oxidizes and becomes brittle. When it does, you can scrape off the peeling portions, prime the bare spots and repaint with latex. Areas that weren't scraped will then peel and, as you repeat the process, your house will eventually be covered with latex paint that sticks.
Alternatively, you can strip the house down to bare wood and start over with latex. This option is the most expensive up front but if done right it can save money on patch jobs and band-aid repainting in the long run. Take this route if you discover widespread paint failure such as aligatoring, cracking or flaking. For blistering, peeling, or wrinkling — which are normally caused by excessive moisture, heat, or humidity — you'll have to correct the moisture that's causing these problems before you can paint the exterior of your house.
Whichever path you choose, remember that painting your house with the best paint over an unprepared surface is like trying to hang a plain piece of paper on a refrigerator without a magnet: it just won't stick.
One final caveat: Lead paint was common until 1950, but was not outlawed in the U.S. until 1978. Do not use any method to remove paint that you suspect contains lead. Call the EPA hotline at 1-800-424-LEAD for more information on lead paint.
Before you begin to paint the exterior of a house, mask windows and doors with heavy plastic or builder's paper and lay drop cloths on the ground. Use a hook scraper to remove loose paint. In spots where wood is uneven, try a putty knife, which is less likely to damage wood. Sand the remaining paint to a dull finish; taper or feather thicker spots. Remove all cracked caulking. Wash the house using your garden hose and awire brush to remove any remaining loose paint. Never use a steel or iron brush, which could leave stains and may glaze the surface.
Then it's time for a primer, paint formulated with a high proportion of binder in order to adhere tightly to wood and to the next layer of paint. Some painters prefer the oil-based variety for its penetration and ability to block the stains that bleed out of redwood and cedar, but I would recommend an acrylic latex to lay the foundation for a lasting paint job. This first coat of primer makes small cracks, nail heads and other imperfections more visible, so you'll want to fill them with a latex caulk and exterior filler, such as a two-part epoxy or a light weight spackle and sand until level. Remember to always prime before caulking or filling. Then mop the house's surface with a damp cloth to remove any remaining dust and apply a second coat of primer.
If you are stripping the whole house down to bare wood, start with a vigorous hand-scraping. When you've scraped as much as you can, patch any gouges or gaps with a two-part wood epoxy. Then sand the entire surface until smooth.
Even the most thorough scraping and sanding won't dislodge mold and mildew in old wood, but a cleaning solution containing a cup of bleach and a cup of trisodium phosphate in two gallons of water should do the trick. Spray the house's surface while scrubbing with a stiff-bristled brush. Let it sit for half an hour before gently rinsing with a garden hose. A power-washer may sound like a time saver but its streaming jets can damage old wood.
Let the house dry for one sunny day and then pretreat the bare wood with a clear, paintable water-repellent to prevent moisture infiltration. Whatever brand you buy, make sure it contains a repellent, often a wax, to help the wood swell less when it rains. Also check the label for a preservative that kills mildew, which can discolor the top layer of paint or cause wood to rot. One to look for is 3-ido-2-propynyl butylcarbamate or IPBC. Repellents not labeled "paintable" may contain so much wax that paint won't stick. Allow this treatment to dry for at least two warm, sunny days before applying primer.
Next you're ready for a coat of an alkyd primer, which has resins that help preserve the wood. After the first coat of primer, seal window surrounds and door joints with siliconized acrylic latex caulk. For the second coat of primer, use an acrylic latex to prime for all top coats.
For old paint in good condition or primed, bare wood, you'll need about one gallon of paint per each 400 square feet. To determine how much you'll need overall, measure the space to be painted and calculate the area in square feet. Divide the area by 400 to get the number of gallons per coat. Rough surfaces like stucco will take more paint so use 200 square feet/gallon for this type surface.
Most paint jobs can be handled with a three-inch straight-edge siding brush, a two-inch angled sash brush, and a two-and-a-half-inch straight-edge trim brush. Good brushes of any size have long bristles with chiseled (tapered) ends and flagged (split) tips. The bristle depends on the paint: natural bristle (hog's hair is best) may absorb water from latex paints, ruining the brush, so they should be used only for oil. Nylon and polyester brushes do not release oil paint uniformly, so these should be used only for latex.
Always start at the top and work down so that any drips are erased as you go along. If you are using oil paint, work it into the wood; latex will level itself out. Paint sprayers provide coverage four to five times faster than brushes, but the finish tends to be uneven, and even with the airless version half the paint drifts away. If you decide to use a sprayer, apply paint sparingly. Two thin coats are better than one thick one.
Although summer, with its endless sunny days and warm weather, might seem like the perfect time for house painting, don't even think about climbing the ladder when the temperature is greater than 90°F. Wait for a day when the temperature will be above 40°F (4°C) for oil paints and above 50°F (10°C) for latex for the full 24 hours. (The number applies to the surface being painted as well as the air temperature.) Painting at low temperatures cause trouble too, making brushing and rolling more difficult, retarding drying, and leaving wet paint susceptible to airborne dirt, insects and pollen.
When you find the perfect day, the best game plan is to "follow the sun around the house." Paint the north side first, the east side of the building late in the morning, the south side in the middle of the afternoon, the west side late in the afternoon. Leave at least two hours for the fresh paint to dry before weather conditions cool to the point where dew forms. If blistering on the wood surface does occur, allow the paint to dry for a few days, scrape off the blisters, smooth the edges with sandpaper and repaint.
You should apply two finish coats, applying each within two weeks of the previous one to avoid the formation of a slick soap-like or chalky substance on the surface. If more than two weeks elapse, scrub the paint with water and a stiff-bristled brush before applying the next coat.
After you've painted the body of the house, proceed to the trim. Oil-based paint is favored for trim work because of its attractive sheen. There is no substitute for brushwork on the trim; it gives you greater control in these small, often intricate areas.
A good paint job should last at least 10 to 15 years, but it's longevity really depends on the location of the house and how well it is protected from sun, wind, and rain. In the end, all of your brushwork will keep your house beautiful and safe. Not bad for a summer's work.