How to Seal Rough Cut Lumber Siding

Jackie Johnson

Using rough-cut lumber as a siding material can be an affordable way to side a building. Sealing the lumber helps preserve it and protects it against the weather, although the sun may discolor unpainted rough-cut lumber even if it has a coat of sealer on it.

Applying sealer to rough-cut lumber preserves wood.

Some find the look of weathered wood attractive, and keeping the wood sealed over time prolongs the life of the wood and protects it against rot caused by humidity or rain.

Existing Siding

  1. Clean the exterior of the building by sweeping off the siding with a broom or brush. Exterior sealers penetrate the wood, so you do not need an immaculate surface, unlike painting.

  2. Find a roller that measures about the same width of the siding to help conserve sealer and avoid drips on the ground.

  3. Pour 1 to 2 inches of sealer into the roller tray. Saturate the roller and apply the sealer to the siding. It may be faster to seal one side or section of the building at a time, since you will not have to move the equipment as much.

  4. Saturate the trim brush with sealer and use it to seal the exposed edges of the rough-cut siding.

New Siding

  1. Lay the siding out on sawhorses or on a horizontal surface to make applying the sealer easier. Butt the siding next to each other so you can cover more than one piece of siding at a time with the sealer. Using a standard-sized roller instead of a short roller speeds the process of applying the sealer.

  2. Pour the sealer into the roller tray, saturate the roller and apply to the siding material.

  3. Stand the siding on its edge after it dries and clamp the pieces together to keep them upright. Apply the sealer to the bottom edge of the siding and remove the clamps once you have coated the edges. Wipe away any drips with a soft, lint-free cloth. Repeat the process to seal the top of the siding and the ends.

  4. Tip

    If you plan to paint the siding, choose a sealer compatible with the kind of paint you may use in the future.


    Avoid using rags that have a nap, like terrycloth towels or microfiber cloths. Rough-cut lumber has splinters that the nap can catch on, slowing the process and depositing lint from the towel or rag on the lumber.