How to Seal Cedar Wood From Moisture

Updated April 17, 2017

Cedar wood makes beautiful lumber and shingles that are popular for use in exterior or wet areas. Use cedar lumber to build decks, fences, other outside construction and shingles (cedar shakes) as roofing and siding material. Essential oils and sap trapped in the wood help prevent rot and protect the wood from insects, particularly termites and other wood-eating bugs. Rainwater will eventually dilute the tannin in the wood and wash out the rich colours, leaving behind a flat, grey look that some find undesirable. Sealing the cedar with a quality sealer will prevent water intrusion and greying and will also help to preserve the natural beauty of the wood.

Remove any dirt or pollen on the cedar by sweeping it with a whisk broom. Vacuum the horizontal areas such as decks to ensure that all dust and debris are removed from the gaps between the boards.

Apply brightening solution according to the manufacturer's instructions to remove the grey look and restore the wood to its original colour. Allow the wood to dry fully.

Test the water content of the cedar wood before applying the sealer. Place a couple drops of water on the wood and observe them. Allow the wood additional time to dry if the water drops stand on the wood's surface. Proceed if the wood is dry enough to absorb the water.

Apply a quality cedar sealant to the wood. Brush the sealer onto small or irregularly shaped areas with a paintbrush. Spray large areas with a garden sprayer and brush over the sealer to force it into the wood grain with a paintbrush.


For best results, use a good quality cedar sealant and apply the sealant to very dry wood. Pick a time of year with very little rainfall to treat your cedar and closely observe the weather forecast before committing to the project. Rain falling onto the wet sealer will ruin the finish and create extra work to fix.

Things You'll Need

  • Whisk (corn) broom
  • Brightening solution
  • Cedar sealant
  • Paintbrush
  • Garden sprayer
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