What if the Deck Cleaner Isn't Completely Removed?

Wood Damage

• Many commercial deck-cleaning products contain chlorine bleach, also known as sodium hypochlorite. Deck brighteners may contain oxalic acid. Chlorine bleach and oxalic acid are harsh cleansers that may strip the wood or weaken the wood fibers, causing damage to your deck. Products that contain sodium percarbonate, a precursor to hydrogen peroxide, are much gentler and less likely to cause damage.

Sealer

• Failing to rinse the deck cleaner off completely may cause problems when you apply a finish or sealer. Chlorine bleach cleaners can cause blotchy spots in a finish, even with thorough rinsing, and residue may inhibit the sealer's ability to permeate the wood.

Exceptions

• Most deck cleaners must be rinsed thoroughly before applying sealers, but borate is one exception. Borate is used to kill algae before applying a sealer. It is not rinsed off but allowed to soak into the wood for two to three days before applying the finish.

Recommendations

• Buy a mild deck cleaner that contains sodium percarbonate, rather than chlorine bleach. Read and follow all package directions and rinse the deck thoroughly to remove the cleaner. The best time to clean and seal a deck is in the spring or fall, when temperatures are cool. Cleaning the deck in the heat of the summer causes unnecessary stress on the wood.