Cleaning a pressure-treated deck should be an annual affair, and if you also have to refresh or even totally restore the finish (see Restoring a Wood Deck), is an important first step. Cleaning a wood deck is simple - just mix a little detergent and a little bleach together in a bucket full of warm water and go at the deck with a scrub brush, right? The problem, though, is that chlorine bleach breaks down lignin, the aromatic biopolymers that make up the cell walls of wood. Bleach also corrodes metal fasteners, and because it is a basic solution, will shift the pH of wood decking away from its natural slightly acidic state.
But there are readily-available alternatives to chlorine bleach - including hydrogen peroxide, oxygen bleach, and sodium percarbonate - that won't damage lignin, are more effective at killing mold and mildew spores, and that won't damage nearby vegetation. Viance - one of the manufacturers of the preservatives that are used to treat wood - has put together a useful summary that breaks down the process and products needed to properly clean pressure-treated wood. The key takeaway? Leave the chlorine bleach under the sink. Read more.
