Wood certainly takes its fair share of beating from the weather and is typically not on the "yearly" list of things to clean. Over time even stained and sealed wood loses its original luster and needs a good cleaning. Some contractors use chlorine bleach to quickly clean the mold and brighten the wood but we DO NOT, UNDER ANY CIRCUMSTANCES, use this method.
We'll wet the wood on your fence or deck first and use a biodegradeble oxygen bleach detergent, (sodium percarbonate), as the first step. Once this has time to dwell then its time for a low pressure rinse to clean the dirt and mold off the wood. Once this step is completed then it's time to neutralize the sodium percarbonate and restore the natural pH of the wood. This is done in step three by applying oxalic or citralic acid to the fence or deck. Once complete, your fence or deck is back to what it looked like when it was new.
Staining and sealing can also be done but is not recommended on the same day of cleaning as we typically like to give the wood 24 to 48 hours to dry.