How long paint and stain last on wood siding

How long a finish lasts depends on the finish, the number of coats and how much sun and rain each wall gets. Walls fully exposed to sun and rain, usually the south and west sides, wear first. Walls protected by porches and overhangs wear slowly and often need repainting only every other time the rest of the house is done.

How long each finish lasts

On wood suited to paint, a primer and one coat of good house paint should last 4 to 5 years. Two top coats can last up to 10 years, so three coats in all last about twice as long as two. One coat of penetrating stain on new wood lasts 2 to 4 years, and later coats last longer, since they soak into the small checks that open as wood weathers. Two coats of stain on rough wood can last as long as 10 years in some exposures. A water-repellent preservative used alone lasts only 1 to 2 years, and a clear varnish in harsh exposure may last barely a year.

The signs a finish needs renewing

• Peeling. Paint peels where moisture gets into the wood.
• Blistering, often in spring. Water vapor from inside the house can condense in the siding over winter and blister the paint when the weather warms.
• Graying. Bare or stained wood that has turned gray needs refinishing.
• Water soaking in. Splash a little water on wood treated with a water repellent. If it beads and runs off, the treatment still works. If it soaks in, the wood needs refinishing.

What a repaint involves

Repainting is ladder work, so have a painter do it. Before the new coat, loose paint is scraped off and the edges sanded smooth, and the old paint is scrubbed and rinsed. Mildew is removed with a dilute household bleach solution. Bare wood is treated with a water repellent, left to dry for at least 2 days, primed and then top-coated. Protected areas such as porch walls need especially careful cleaning, since they collect residue that keeps new paint from sticking. Stained siding is easier to renew: it's brushed clean of dirt and loose fibers and given a new coat.

Rags wet with oil-based stain can catch fire on their own. Bury them, soak them in water or seal them in an airtight container right after use. Never mix bleach with ammonia or with a cleaner that contains it, since the fumes can kill.

An annotated example

What to do next

Look over the siding from the ground once a year, starting with the south and west walls, and splash-test any wood treated with a water repellent. When the paint peels or blisters, or the wood grays or soaks up water, book a painter, and ask for the walls in full sun to get two top coats.