How to Clean Fungus and Mold off Duradek Vinyl Deck Membranes

Any permanent outdoor surface needs to be cleaned from time to time, and your vinyl deck is no exception. While the benefits of having a vinyl deck include no sanding, staining or re-coating of any kind, your deck will look its best with a seasonal cleaning (about 4 times a year).

Sometimes, however, there are contributing factors in your environment that may cause you to require more than a general cleaning on your deck's surface. One of these factors is mold and fungi which in some areas under certain conditions can be a troublesome maintenance issue like that experienced by some homeowners in Florida experiencing green and black growth on their metal roofs.

The bottom line is that it is difficult, if not impossible, to control all of the factors that contribute to mold growth and your best defense to keep your vinyl deck clear of fungus and mold is a general cleaning 4 times a year.

Step One - Start With a General Cleaning

Ideally, your vinyl deck should be cleaned at least four times per year (more often if acid rain or airborne pollution is a problem in your area) using Duradek vinyl cleaner which is available from your authorized Duradek contractor or directly from Duradek. Follow the directions on the label.

This cleaner is designed for vinyl and will NOT leave a harmful chemical residue like many household cleaners may. Use warm water and a stiff broom, scrubbing in a circular motion to loosen the dirt. Spray with a garden hose (under pressure) to wash away the loose dirt. Flush thoroughly with clean water.

Note: It is very important to remove all residue from cleaners used on your deck. While the cleaner itself may be gentle enough, it is when the sun 'bakes' the chemicals into the surface that your deck can experience discoloration.

Step Two - Mold and Fungi Removal Recommendations

Sooty Mold - Image from USDA Forest Service.

Both Artillery Fungus and Sooty Mold have similar cleaning procedures. For plastic and painted surfaces that might have sooty mold, the USDA recommends:

• 1/3 cup powdered household detergent
• 1 quart household liquid bleach
• 2/3 a cup of Trisodium phosphate
• 3 quarts of water
• (be sure to use rubber gloves when cleaning with this solution)

Clorox® recommends using their "Outdoor Bleach" product diluted at a rate of 1 part Outdoor Bleach to 6 parts water, as per their recommendations for cleaning vinyl surfaces. Apply early or late in the day when the membrane surface is cool to the touch. Apply solution with a garden sprayer and allow to sit on the surface for a minimum of 10 minutes. Re-apply the solution to areas that begin to dry during this period.

Use a soft bristle brush on a pole to scrub the membrane surface. Small remaining spots can be cleaned using a firmer bristle brush. Then rinse the entire area thoroughly with a garden hose.

Note: at the time of publishing this article, Clorox® Outdoor Bleach is not available in Canada. When using any cleaner, make sure the manufacturer recommends their product is suitable for outdoor vinyl products and their written instructions are followed.

Sooty Mold on vinyl deck - before cleaning.
Photo by Duradek MidAtlantic.

Duradek vinyl deck - after cleaning off sooty mold.
Photo by Duradek MidAtlantic.

Details on Common Mold and Fungus

Artillery Fungus are dark raised spots about the size of a pencil tip that do not melt into a larger circle. For further information on how to control established Artillery Fungus in ground cover, see this document from the Penn State University website.  

Sooty Mold is a dark fungi which leaves dark spots or darkish areas which look like, well, soot. For further information on how to control Sooty Mold, go to Virginia Tech website.  

If you are experiencing hard-to-remove mold on your deck, you may be interested in reading this excellent case study that was conducted by Duradek distributor, Duradek MidAtlantic which documents the diagnosis and removal of Sooty Mold.

Refer to Case Study - Diagnosing and Removing Mold From Duradek

See also, Duradek's Care & Cleaning Recommendations for your Duradek Vinyl Deck.