This is a common problem that many people face. Often it occurs because people are looking to cut cost and working hours on projects. As a result, the wood is left exposed and begins to turn gray. Luckily there is a solution. There is many products on the market that can solve this problem for you.
Clean and Brite by TimberPro is our most recommended solution for the problem. It uses phosphoric acid to strip the weathering end dirt from the surface of the wood. It also removes dirt and mold. It is quite effective as you can see from the sample below.