For years bleach has been used as a homemade alternative for cleaning wood or mildew and also as a lightening agent. It does a good job of killing the mildew but in my opinion it takes away the natural pigment of the wood. Also, if you plan to use a power washer you will be interested to know that in my experience the bleach softens the redwood fibers. This is a form of damage. When the power washer is then applied, the damage becomes very apparent by washing away the surface of your wood. For these reasons I do not recommend the use of bleach on wood.
    Many times when a homeowner removes the planted pots from their deck a ring has formed on the surface of the deck. On occasion the pot had been there so long that the wood underneath has begun to rot away. How can a deck owner avoid this problem? Since this is caused by trapped moisture between the deck and pot simply place something between the plant and pot so air can get between. At any home and garden shop pot holders are available to lift the pot off the deck. Some have wheels for those heavier pots. I’ve even seen some people place 3 or 4 small flat stones between the deck and pot. This is a quick and simple cure for this problem.
    What I have found to be helpful for the deck is to make sure that all plants growing alongside of the deck be trimmed. The plants by nature will hold moisture against the wood. This will promote mold, mildew and ultimately rot.
    I have always found it interesting that the fasteners used will loosen and begin to come up. Even if they are fastened with the best deck screws. I don’t really have a solution but it may make you feel better to know that even the most expensive decks are having the same problems. Once a year you may want to take the time to refasten them by tapping down the nails or drilling down the screws.     When looking for a deck finish that looks good, lasts, and then can be cleaned and reapplied after 2 to 4 years, never use a shell coating. That is a finish that acts like paint by coating the wood. Always use an oil that is absorbed into the wood. This way your wood will get protection from inside out. Also in my experience I have never found a clear finish that lived up to its guarantee regarding color fastness. They provide little to no protection from U.V. since the protection comes from the pigment. Our experience has been that 3 to 6 months the wood has faded back to a gray tone. We use only oils that are pigmented. We never use clear finishes.
     When looking for a deck cleaning contractor find someone that specializes in cleaning and treating exterior wood. I can’t tell you how many jobs I’ve been call to where the homeowners wanted to cry. With in days to weeks their deck was already turning dark or sticky. I’ve been to homes where the finish is on the house and plants. Sometimes the finish may already be fading with no water repellency. When questioned they used their gardener, landscaper or friend. Even building contractors and painters have a difficult time with cleaning and treating decks. They understand building and painting but know very little about deck finishes and how to apply them. Always use a licensed contractor that fully understands not only their products that he will be using but also and those that are out there. Please, save yourself a lot of stress and money. Lic#B883139