The short answer
Many wood fences need stain or sealer every two to four years, but the right interval depends on the product, lumber, sun, moisture, and exposure. Inspect the finish yearly and recoat when water soaks in readily, color fades unevenly, or bare wood becomes exposed.
Use the fence condition as the schedule
A fixed calendar is only a starting point. South-facing sections may weather faster than shaded areas. Sprinklers, vegetation, and snow storage can expose the lower boards to more moisture. Check several areas instead of judging the entire fence by the best-looking panel.
A simple water test can help. Sprinkle water on clean wood. If it beads for a while, the finish is still resisting moisture. If it darkens and absorbs quickly, cleaning and recoating may be due.
Preparation affects the result
Do not coat over heavy dirt, mildew, loose finish, or wet wood. Clean the surface using a method suitable for the lumber and product. Allow it to dry fully, make repairs, and follow the finish manufacturer's temperature and weather requirements.
Aggressive pressure washing can damage soft wood fibers and create an uneven surface. More pressure is not always better. Test a small area and use cleaners and tools appropriate for the fence.
Stain, sealer, or paint
Penetrating stain adds color while allowing the grain to show. Clear or lightly tinted sealer focuses on moisture resistance but offers varying ultraviolet protection. Paint creates an opaque film and a distinct look, but peeling preparation can be more involved later.
Use a product made for exterior fencing and compatible with any existing finish. If the current coating is unknown, test adhesion or ask a professional before covering the entire fence.
- Inspect yearly for exposed wood and failed finish
- Keep sprinklers and soil away from the boards
- Repair loose boards before coating
- Choose a dry weather window for cleaning and application