Mold on a Deck or Fence

Mold grows along surfaces and requires moisture and a nutrient source. Since decks and fences are outside, there is plenty of moisture supplied by rain and humid air. And there are lots of biological nutrients in the natural environment in addition to the wood itself – like dust, pollen, leaves, flowers, etc. – that can end up on a deck or fence. If you use your deck for entertaining or family meals, food and beverages that provide both moisture and nutrients for mold growth may be spilled on the deck surface.

Breathing dead or living mold spores can cause health symptoms, so it’s not a good idea to live amidst mold growth. You don’t live full time on your deck, but if you have young children, they may be crawling over or playing on the deck. And a moldy fence may be a cosmetic issue. So if there’s mold on your deck or fence, it’s a good idea to get rid of it.

With the exception of soft-rot fungi that decay fence posts or pickets in the ground, the kinds of mold commonly found on decks and fences do not degrade wood-cell structure. There may be wood-decaying fungi present, however, if your wood deck or fence has been wet for extended periods of time and water has soaked into cracks or the wood grain. If you find soft or rotted wood or see mushrooms, have a contractor evaluate the deck or fence and complete required repairs. In the meantime, stay off the deck in case it’s so damaged as to be unsafe.

What Isn’t Mold?

People often mistake algae and moss for mold growth. Algae and moss are “leaf green” in color and grow in areas that are consistently damp – like deck surfaces that are in shade or are subjected to roof water, the bottoms of fences that are dampened by rain and ground water, or on the outside of foundation walls where rainwater and roof water splashes frequently up against the building. Algae and moss are unsightly and can be slippery to walk on.The Trask Product, Oxy-Mold, is useful in getting rid of stains from these organisms as well as in cleaning away mold.