How to Waterproof Wood Posts

Waterproofing a wood post slows the post's absorption of moisture. A waterproof wood sealant can also improve the appearance of the wood post by adding shine and color. "By reducing the periodic wetting of wood, water-repellent coatings can reduce the swell-and-shrink cycles that contribute to the checking and weathering of exposed wood such as decking boards," according to Adam Taylor, assistant professor of forestry, wildlife and fisheries at the University of Tennessee. Waterproof wood sealants can be purchased at local hardware stores.

Preparation and Application

Waterproofing a wood post near a water source extends its life.
  1. Sand the wooden post to expose the natural timber. Wood posts can be pretreated or varnished. By sanding the wood, the waterproof sealant absorbs directly into the wood posts.

  2. Dust the debris from the wood post using a rag. Leftover debris blocks the waterproof wood sealant from absorbing into the wood post.

  3. Pour 8 ounces of waterproof wood sealant into a paint tray.

  4. Apply the waterproof sealant to the brush. Brush a thin layer of waterproof sealant over the entire wood post.

  5. Let the waterproof sealant dry for 12 hours.

  6. Repeat Steps 3 to 5. To effectively waterproof a wood post, three coats of waterproof sealant are needed.