How to Waterproof Wood for Below Grade Use

Wood used for purposes below grade is susceptible to water damage and decomposition at accelerated rates if left unprotected.

Protect wood below grade with a waterproof sealant.Protect wood below grade with a waterproof sealant.
With the application of a below-grade waterproof sealant, you can ensure that the wood remains protected for many years and forget about compromising the structural integrity. For those new to the process, applying the sealant is a quick process that can take less than 30 minutes to complete.

Remove the top of a general-use pump sprayer or a garden sprayer and insert a funnel into the opening.

Protect your hands with rubber gloves and your eyes with safety goggles.

Carefully empty the contents of liquid wood sealant into the pump sprayer. The sealant should be rated for "below-grade" purposes.

Secure the top on the pump sprayer and prepare it for use as directed in the user manual.

Hold the wand of the sprayer 6 to 8 inches away from the wood surface and apply the sealant to the wood with long, overlapping strokes. Be sure to cover all surfaces of the wood that will be covered below grade with the sealant. Wait 24 hours for the wood sealant to dry before installing the wood.

Things You Will Need

  • Wood sealant (below-grade rated)
  • Funnel
  • Pump sprayer
  • Safety goggles
  • Rubber gloves