A thorough scrubbing is a must before painting any exterior surface. It removes the dirt and broken-down paint residues that keep fresh coats from adhering and gets rid of mildew that grows on paint in all but the most arid climates. Most contractors clean with pressure washers, but in the hands of someone unfamiliar with the equipment, these can gouge wood, shatter glass, and drive water behind siding and trim. Using a hose, a pump sprayer, and a scrub brush is slower but safer, and just as effective.

Paint that has peeled, bubbled, or blistered has got to go. Scrape and sand all cracked or chipping paint. Lead Alert — there’s a strong possibility in houses built before 1978 that lead may be present in old paint — you need to proceed with caution. If your paint does contain lead, you’ll need to take special precautions during the scraping and sanding phases to protect yourself, your family, and the environment from toxic dust. If the paint is lead-free, you ‘ll need a dust mask and lay down tarps to catch debris before tackling the most crucial part of the project.

After the sanding is done, it’s time to fill minor cracks and dents, repair any rot, and replace any pieces that are too far gone.

Primers are formulated to penetrate, seal, and provide a good surface for the top coats to stick to. Use them over bare wood, Spackle, and epoxy, or over paint with a chalky, deteriorated surface. Acrylic primers can be used on most surfaces, but on cedar or redwood, oil-based coatings are a must because they lock in these woods’ reddish-brown “extractives,” which will leach out and leave behind rusty stains if the wood is primed with a water-based product.

Spray exposed nail heads with a metal primer to prevent rust from bleeding through the paint.

When the primer is dry, caulk all small joints (less than ¼-inch-wide) in the siding and trim.

Deciding which paint to use has gotten much easier now that acrylic latexes have pushed oil-based paints almost to extinction for painting exterior walls. The acrylics offer superior performance (they don’t harden with age, the way oils do, so they move and breathe without blistering), they don’t mildew as readily, and they emit fewer VOCs, so they comply with new air-quality regulations. They also work over both oil- and water-based primers. Oil paint still has a place in high-traffic areas such as wood steps and porch floors because of its superior wear resistance and on steel and cast-iron railings, which benefit from oil’s water repellency. Start at the top and work down. Work in the shade, out of the sun’s glare. As the dance proceeds, keep an eye on the weather. Rain can wash freshly applied latex right off the wall, and a temperature dip below 10 degrees celsius two days after application can interfere with adhesion and curing and dull the sheen of glossy paints.