Just about any exterior stain will make your house look good for a few years. But the best products on the market can maintain their looks for as many as nine years, according to our ongoing tests.
We test products by applying two coats of white, red and green versions of each stain (where available) on unprimed sections of wood siding. We then leave the boards outdoors on racks angled to catch the most sun. Each year for three years we evaluate the stained boards to judge how much their appearance has deteriorated, since a year of that kind of severe exposure is equivalent to about three years of normal exposure to the extremes of sun, rain, wind and temperature.
We test exterior paints much the same way, applying two coats of white, blue and brown paints to primed boards. The colors we chose for paints and stains represent not only widely used house colors, but also broad families of hues and different types of pigments, which react to weathering in different ways.
In general, paints held up better than stains over the course of our testing. Both will change color in sunlight and can accumulate dirt and mildew. Mildew can be a problem in damp areas, from rainy Seattle to steamy Tampa, or on any house that gets more shade than sun. Baking in bright sun, meanwhile, can change even the best-quality pigments. Blues and yellows are the most likely to change.
We have found that the best type of stain is opaque, or solid color. Opaque stains are the type that covers the wood grain completely. They're often called solid stains in ads and on the cans. Semitransparent stains, which let some wood grain show, aren't as durable. After no more than two years (about six actual years) into our tests, their appearance and ability to protect the siding has deteriorated to the point at which a fresh coat of stain is needed.
As a rule, water-based latex stains are easier to work with than oil-based alkyd stains be cause they clean up with water.
At the end of our three-year cycle, two opaque stains stand out as best for the long term, based on overall performance of the three colors tested. Olympic Premium 596xx ($18 per gallon) and Behr Plus 10 ($18, from Home Depot) were among the best-looking of the fully tested products, and so will last the longest in actual use. The two are closely matched, al though the Olympic has an edge in resisting color change. (It's a latex stain, while the Behr is an alkyd that nonetheless cleans up with water.)
If your siding requires a semi transparent stain, we recommend the Olympic Water Repellent 511xx, an alkyd that sells for $18 a gallon. We stopped testing this stain early because its appearance had deteriorated too much. But this is the best choice if you sided the house with a wood such as redwood and want some of the grain to show. Just be prepared to apply new stain more often than if you used one of the recommended opaque stains.
Another opaque stain that held up well after our three-year test cycle was Sherwin-Williams Woodscapes Solid A15, a water- based latex ($29). However, this stain has been reformulated since our tests -- manufacturers regularly reformulate their products to improve performance, cut costs or comply with environmental regulations -- and the version now in stores may not perform the way the version we tested did.
Before you apply stain (or paint, for that matter) to your home's exterior, be sure you scrape, sand and clean the siding thoroughly. Good preparation makes the covering last longer. So does applying two coats.
By the editors of Consumer Reports at www.consumerreports.org.