How to Remove Mold and Mildew from Trex


Eli asked: How do I clean Trex boards? The “maintenance free” Trex builds mildew and black spots. What would you recommend to clean with?

Trex boards offer a wonderful, low maintenance option for decking. Although the boards require less maintenance than regular wood, they do require some care to keep them looking their best. Fortunately the cleaning methods are simple and do not require special equipment.

You Will Need:

  • Deck wash with bleach and detergent (ex: Olympic Deck Wash or Expert Chemical™ Composite Deck Cleaner & Enhancer)
  • Scrub brush
  • Water

Steps to Remove the Mold and Mildew:

  1. Unlike many cleaning projects, when cleaning Trex, we will start with the boards being dry. Applying the deck wash on wet boards will reduce the effectiveness of the wash.
  2. Prepare the deck wash, following the instructions on the package. Some washes can be used directly from the package while others require dilution.
  3. Apply the deck wash to the surface of the boards.
  4. Scrub the moldy areas with a scrub brush.
  5. Rinse the area completely with water to remove all of the deck wash and loose mold particles
  6. Repeat until all of the mold is removed.

Additional Tips and Advice

  • While pressure washers may seem like an easy fix, they are not recommended by the Trex company. Using a pressure washer with high pressure or too closely will result in voiding the warranty.
  • There are bleach-free deck washes available as well (ex: Corte-Clean Composite Deck Cleaner) that will also remove mold from Trex.
  • Regular cleanings will be necessary to keep mold from returning.
  • Mold is an eyesore on decking, but it does not damage the Trex like it does wood. It simply grows on the surface.
  • Clean the boards regularly with soap and water to remove dirt, pollen, leaf debris, etc. These items feed mold and cause it to grow more rapidly.


  1. Bob says:

    I bought a house several years ago that had TREX decking. I found out that the former owners were very lax on maintenance throughout the inside as well as outside of the home. The following year I took on the cleaning of the deck with detergent. While this did clean the deck somewhat, I still had disgusting mold in many areas. I used a bleach solution on the dry deck, in some places more than once, and the decking is now beautiful. I will keep this deck clean and mold-free every year by doing the above cleaning.

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