Mold is a natural environmental occurrence. If the conditions are right, it can show up almost anywhere – on wood, vinyl, sheetrock, or even decking. It’s not a product defect, so it’s rarely, if ever, covered under most product performance warranties.
Mold can occur on almost any material, including wood decking and uncapped composite decking.
There are steps you can take to minimize the likelihood of mold growth. Mold is much more pervasive on wood and uncapped decking products, so choosing a capped composite deck board is a smart first step. “Cap” is a common industry term used to describe the protective outer layer that surrounds the wood-plastic core of the deck board.
What causes mold?
Most often, mold results from airborne pollen, fertilizer overspray, or leaf litter (although not exclusively). Mold spores are lightweight and become airborne easily. If they are in the surrounding environment — the eaves of a home, the roof, or a fence, for example — they can settle onto the decking. Once there, it takes only a few key ingredients for the mold to grow.
How does mold grow on decking?
To thrive, mold and mildew need four things: air, water, 40°-100° temperatures, and a food source. Leaves, debris, pollen, and other organic materials are an excellent food source for mold development, so it pays to keep your deck clean. Even so, there is no way to completely eliminate all of these environmental conditions.
The porous nature of decking aids the process, as mold spores will settle into these pores and root. Once moisture, heat, and a food supply are introduced, the spores will bloom and create dark spots on the boards. Eventually this will spread across the deck. If the boards are not thoroughly cleaned of mold and its rooting, the mold will return — especially if it is prevalent in the environment around the deck.
Clean your deck regularly to minimize mold
To minimize mold on the decking, clean the deck as often as needed but at least twice each year. Climate conditions vary in different regions of the country and may necessitate more periodic cleaning. In some situations, you may need to repeat the cleaning process multiple times until you are no longer able to see any “shadows” of the spots on your deck while it is wet. You would also want to apply a mold inhibitor to retard future growth. Once the decking has been thoroughly cleaned, you will need to maintain it in much the same way you would adhere to a cleaning schedule for any other significant item in or around your home.
Should a deck with mold be power-washed?
No. Power-washing will only worsen the mold problem. The pressure of the power washer actually pushes the mold further down into the pores of the material. We DO NOT recommend power washing the decking while mold or mildew is present. If a pressure washer has been used, we recommend at least two applications of cleaner to ensure that the roots of the mold are thoroughly neutralized. A pressure washer can also, if used improperly, damage the deck surface. We recommend exercising extreme caution when using a pressure washer for deck cleaning. Remember to keep the tip at least 12 inches from the deck surface to prevent damage.
Source: https://www.fiberondecking.com/blog/how-to-minimize-and-prevent-mold-growth-on-decks/
