Wood siding, unlike vinyl or metal, requires protection from the rain, wind and sun. This means applying paint or stain
to new wood and periodic re-coating on previously finished siding. When re-finishing previously finished siding, it’s usually easiest and most economical to stay with the previous finish. If you want to enjoy the character of new wood, you’ll achieve the best results with stain.
Opaque stains behave much like paint, forming a surface coating that is thinner than paint but generally more durable than penetrating stains. Semi-transparent penetrating stains allow the full texture and grain of the wood to show but are more sensitive to weathering. To improve their performance, many semi-transparent stains include a UV (ultraviolet) blocking pigment. This allows the full beauty of the wood to show through while increasing the longevity of the stain by protecting it from the sun. See also Outdoor Stains & Paints
Whether painted or stained, wood siding needs periodic attention. Siding that is primed and coated with one or two coats of good quality exterior paint
may last a decade or more and require only a periodic hosing off with a garden hose or very gentle pressure washing. Letting algae or lichens build up on painted siding will shorten the life of the coating. It’s not hard to tell when it’s time to re-paint. The peeling and blistering paint is hard to miss.
With penetrating stains, knowing when to re-apply takes a little more investigation. Most semi-transparent stains, even with UV blockers, will fade over time. Compare areas that receive full sun with fully shaded areas to judge the amount of fading. You can also test the integrity of the finish by spraying with a garden hose. The surface should shed water easily. Dark patches of siding indicate the wood is absorbing water and should be re-stained.