How To Clean Mold From A Composite Deck

rhino hide composite decking

Many choose composite decking for their home because of the long lasting materials, low maintenance, and beautiful designs. When black or green mold spots begin to appear, it can be very disappointing. All the misguided advice floating around can just add to the frustration. How can you easily clean a moldy deck, and more importantly, keep it from coming back?


How to Remove Mold From Your Deck

It is always a good idea to check with your manufacturer for recommendations. For instance, TREX® Composite decking recommends UltraMean2 as an eco-friendly alternative to many of the other harsh “deck cleaners” on the market. A common misconception when dealing with a moldy deck is to use Chlorine Bleach to clean it. This is NOT a good idea. Click this link to read why you should never use Chlorine Bleach to clean a composite deck.

The best solution for composite decking is a sodium percarbonate based cleaner, such as UltraMean2. It will provide you with a deep clean without damaging the deck.

How To Clean With UltraMean 2

What you will need:

  • UltraMean2

  • Pump Sprayer

  • Bucket for mixing and something to stir with

  • Soft bristle brush with long handle for scrubbing

  • Hose

Step 1:  Remove any patio furniture from deck and sweep to remove dirt and debris.

Step 2:  Start by mixing a small solution of UltraMean2 and clean water (warm or hot water preferred, but not necessary). Mix until completely dissolved. Some foaming is normal. This first solution will help you determine the cleaning strength you need. The label suggests 2-5 capfuls per 1 gallon of water for a medium duty clean and 4-8 capfuls for heavy duty cleaning. Starting on the weaker side, you can follow the next few steps and try cleaning a small area. If you determine that more concentrate is needed, just add more powder to your cleaning solutions and try again.

Step 3: Pour mixture into pump sprayer and apply to one area a deck liberally. It is best to work in one area at a time, because a wet deck can get quite slippery. As it cleans, you will see foaming action. This is the product working to clean deep inside the deck. Keep the area wet for at least 10 minutes. If it begins to dry just spray it again.

Step 4:  Scrub with a soft-bristled brush. You may notice the white foam turning black or grey, especially if your deck is very dirty.

Step 5:  Rinse with clean water. If you are satisfied, move to the next section of deck. For tough stains, spray again with fresh cleaner and let the solution sit on the deck longer. An oxygen bleach works best when allowed to sit for 20-40 minutes.  Scrub again and rinse. For stubborn areas, you can sprinkle some of the UltraMean2 powder onto the wet surface and scrub.

Step 6:  After the remaining sections of deck have been cleaned, allow to dry. If the deck was not rinsed thoroughly, a white residue will appear when dry. This is harmless soda ash and can be swept or hosed away.

How To Keep Mold From Coming Back


Composite Deck Maintenance Kit

Want to skip the store? We gathered up all the cleaning essentials to get you started with our ready-to-go kit.

Cleaning a deck can be time consuming and hard work. Fortunately, that heavy duty cleaning can be avoided. If you use UltraBan Mold Barrier properly you may be able to retire the scrub brush. UltraBan is a unique formula that will penetrate the deck and create a protective invisible film that mold cannot grow on. Yes, it is completely invisible and will not change the look of your deck. You will only know it is there because mold hasn’t come back!

Regular weathering and traffic will not remove UltraBan’s invisible film. Even in harsh climates you can expect UltraBan to last for a year or longer! Once a year, do a light duty cleaning (detergent and water) and reapply UltraBan. Throughout the year, light duty maintenance such as regularly sweeping or hosing dirt or debris and cleaning up food spills immediately will keep your deck looking great.

Is using UltraBan hard? Not at all!

How To Apply UltraBan

You will need:

  • UltraBan ( 1 gallon will cover approximately 300-400 sq. ft. of composite deck.)

  • Pump sprayer

  • Clean sponge mop or something similar

Step 1:  Pour UltraBan into clean pump sprayer. DO NOT add water.

Step 2:  Spray surface to saturation. Apply to a completely dry deck for best results.

Step 3:  Keep wet for at least 15-20 minutes. If it starts to dry, spray again. It is best to do this application in the shade or when it is overcast to prevent the surface from drying too fast.

Step 4:  After about 10 minutes wet the sponge mop with UltraBan and wipe the surface once or twice. This will prevent pooling and ensure an even coverage.

Step 5:  Allow to dry. Once dry, you can relax! Your deck is now protected from mold. Repeat once a year for long lasting protection.

Need more? Visit our decking how-to page for more detailed instructions!