Why do decks and fences turn gray and green here?
Wood outdoors takes a beating. Sun and rain break down the surface and turn it silver gray. In a humid place like Greensboro, damp wood also grows mildew and algae, especially on shaded decks, north-facing fences and boards near the ground.
Typical problems we see on wood:
- Green or black mildew on shaded boards and rail tops.
- Slippery algae on steps and low decks.
- Gray weathering where old stain or sealer has worn away.
- Tannin stains from leaves, and rust marks around fasteners.
- Yellow pollen film in spring that settles into the grain.
Many local decks and privacy fences are made of pressure-treated southern yellow pine, which weathers quickly if it is not maintained. Cleaning helps it last longer.

