This south facing wood balcony wall gets indirect light, but no direct sun. The graying, which ultimately will turn black, is happening because a topical sealant has been used over the years, vs. using a transparent stain. Topical sealants, although they do protect the wood, also magnetize an extra-ordinary amount of natural debris. Because sealants can remain sticky(especially with limited sun exposure) you can see how and why the wood can turn grey and then black.
To prevent this from happening to wood siding or shingle siding, it’s important to properly wash the wood boards and consistently maintain the wood with quality transparent stains. This picture is evidence as to how well dirty siding will clean up with the right kind of pressure wash. No lap marks and no more greying. The work isn’t done though. The next step is to apply Biowash Natural Deck Oil.
