Trex Deck Information

TEL 540.542.6300
FAX 540.678-3002
September 19th, 2011
Mold Technical Bulletin
Mold is a lower form of plant life that can settle and grow on any surface, including Trex® decking. Mildew is a form of mold that grows on damp surfaces.
Mold spores are similar to seeds, but cannot be seen until colonies form. Air currents, insects, animals and water transport the spores easily. Due to mold’s adaptability and large number of species, it is very hard to control and impossible to totally eliminate. Mold will not affect the structural performance of Trex decking.
In order to form visible colonies, mold needs food, moisture, and temperatures between 40 and 90° F. Trex decking is not a food source for mold, but can collect food in the form of dirt and debris such as the overflow from flowerpots and gutters. Trex decking can also supply moisture if the gaps between deck boards are too small or clogged. Refer to Trex decking Usage Guidelines for gapping instructions.
How to remove Mold from Trex® Composite & PVC Decking
All exterior building materials require cleaning. Trex is no exception. Periodic cleaning of Trex decking will remove dirt and pollen that can feed mold. If mold colonies appear, clean the deck with a commercial deck wash containing a detergent and sodium hypochlorite, commonly known as bleach. This chemical will remove the mold, but please be aware it will also lighten the wood on the surface. In some cases it will require several treatments with the deck wash to completely remove all mold colonies. Even if the spots are no longer visible, there may still be mold spores on the surface that could re-grow, so periodic cleaning is important.
The following brands of deck cleaners have been found to be effective in removing mold from Trex decking:

Olympic® Premium Deck Cleaner*

Expert Chemical™**Composite Deck Cleaner & Enhancer (
Always apply these products to a dry deck. Applying to a wet deck will significantly reduce the effectiveness of the cleaner. NEVER mix any other cleaners (ammonia, phosphoric acid, etc.) with bleach.

For a non-chlorine based alternative UltraMean®**** can be used, but will require scrubbing with a soft brush immediately after application.
Mold spreads easily and may return in some environments despite proper cleaning and preventative measures. Mold does not damage Trex and will cause no structural harm if allowed to propagate.
How to remove Mold from Trex Transcend™ Decking
If debris such as pollen and dirt is allowed to remain on the deck surface, mold can feed on the biofilm. Using


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