As with any coating, longevity depends on good preparation and application. Professional painter Rich O'Neil offers his advice for putting penetrating stains on decks and siding.
1. Don't Delay
If you see a spot of bare wood or notice fading, get right to work. If you wait too long, you'll have to sand out the gray discoloration before you start.
Wet the wood with a hose, then apply a cleaner like Jomax. Let it sit a few minutes, then scrub with a stiff-bristle brush to loosen the dirt. Hose off the debris; don't use a pressure washer, which can gouge wood. Pull out any gunk between boards with a 5-in-1 tool. On vertical surfaces, work from the bottom up.
When the wood is dry, rough up the surface with a random-orbit or pole sander fitted with 60-grit paper. Use a leaf blower to blast off the dust.
O'Neil favors a thick, 4- to 6-inch block stain brush, like the one here, which gives him better control than a sprayer. To prevent lap marks, work on only two or three boards or courses at a time and go from one end to the other. If spraying or rolling on the finish, always go back and brush the surface.
After 20 minutes, mop up any stain that hasn't penetrated. To avoid spontaneous combustion, put stain-soaked rags in a sealed can filled with water. Dispose of the container at a hazardous-waste center.