Tom,
A few years ago I was preparing to speak at a PWNA wood restoration seminar, I called the US Dept of Agriculture, Forest products division and told them that I would like to put an end the the age old argument regarding washing wood. The first thing I was told was that they spend all their time doing nothing but testing wood and chemical reactions, and that they didn't like guys like you and I, (pressurewashers) They said that nobody should powerwash wood, I told him that I promoted washing with low pressure. He said that the best way to wash wood was bleach water & spic n span, he said he suggest two people on the deck one apply bleach solution 3-4 % the other to immediately scrub with a push broom let sit no more thet 5 minutes then rinse with a garden hose, then neutralize. I started using this method, what a wonderful difference it made , decks were cleaner, brighter, accepted sealer better, not to mention the fast in & out my crews were.
the cost per deck was incredible, my profit margin increased. We have been using this method for years, and have never damaged the wood. There are sealer manufactures out there who do recommend washing a sealed or unsealed deck with bleach you may have only called those that don't. Remember that another reason some companies don't condon this practice is that there is no control of the strengh that somone might use and risk hurting the wood or the sealer. Also washing unsealed gray wood and washing a sealed deck are two different things. Also don't forget how important a maintainance program is. If you don't have one... I'll be glad to help. Tom, You certainly can run your business and your washing techniques anyway you feel. But when you increase your productivity and bottom line this much it's worth a try. Thank, and sorry for being long winded, Good luck. Chris Detter/ Atlanta