Do I Need to Bleach a Deck Before Re-Staining?

Mold and Mildew Removal

• One of the primary reasons for bleaching a deck is to remove mold and mildew. Hosing or regular cleaners may wash mold away, but it will regrow without bleach to kill the spores. Keeping a deck free from mildew also helps preserve the wood. Decks that have had linseed oil on them are especially prone to mildew problems, and often require bleaching to permanently get rid of the mildew. To make a homemade mold and mildew bleach solution, the University of Tennessee Knoxville recommends mixing 1 quart of bleach, 1/3 cup of liquid laundry detergent and 3 quarts of water. After bleaching the deck, consider restaining with a finish that contains a mildew prevention agent.

Lightening the Wood

• After removing the old stain, bleach the wood on a deck to lighten the color. Some people apply bleach to naturally dark woods to make them light tan or even white in color. Buy a commercial wood bleach, or make a homemade bleach solution to lighten the color of the wood. The U.S. Forest Service recommends several homemade bleaching solutions, including a simple mixture of 1/2 pint of laundry bleach in 1 gallon of water.

Removing Dark Patches

• To remove dark patches from old stains or natural patterns in the wood itself, carefully apply bleach only to the dark areas to lighten them. Bleach can also help remove dark patches from glue or solvent stains. Bleaching dark spots is not usually required for a new finish to work properly. It may, however, be necessary to end up with an even color underneath the new wood stain.

Bleach Application Technique

• Wear gloves when applying bleach solutions, because they can damage the skin. For most home projects, a sponge or brush works well to apply bleach to a deck. Some people use sprayers for very large projects, but they make it difficult to apply bleach to small dark spots. Cover the part of the deck that needs lightening with the bleach solution, let it soak in and lighten the wood to the desired color and then rinse the deck. Allow the wood to dry thoroughly before restaining the wood.