But don't go overboard. Otherwise, it will damage the wood by raising the grain and causing the wood to fur. Even brand-new decks should be thoroughly washed before treating, said Mendenhall. We train our contractors to think about whether they should clean the wood or strip it first. We train them to throw water on the deck, to see if there's already a water-resistant coating on there.
Time is money.
The products' costs are fairly insignificant. Contractors tend to skip on cleaning steps, and give quotes that are too low in order to snare customers. They'll get someone with very minimal equipment to save money, as opposed to someone with professional equipment to do a proper cleaning. To do it right, you need to clean, wait three or four days, and then go back to finish the job. Older decks in particular, Marsh said, need extra preparation time.