What Is the Black Stuff on My Deck

The biggest reason for a deck stain turning black is mildew. All wood surfaces need to be cleaned correctly prior to staining. … Mildew can begin to grow underneath the deck stain, which causes discoloring. This can also lead to rot and decay because if there is mildew there is also moisture present.

How do I get rid of black mold on my wood deck?

To remove black mold from deck wood, apply a solution of ordinary dish soap and water to the deck, scrub it with a scrub brush attached to a pole, spray it clean with a hose, then spray the deck with vinegar to prevent new mold growth.

What does harmless black mold look like?

Black mold, as the name implies, is often dark in color. When searching for black mold, look for circular-shaped spots that are black, dark green or dark brown. Some black mold can also take on shades of orange or have flecks of white within it. Most of the time, black mold has a slightly furry appearance.