Composite decks were supposed to be maintenance free and last forever, that’s why everybody spent the extra money on composite decking instead of a traditional wood deck.
Now it seems that we been “had” , they do get dirty, mold spots show up all over the deck like a case of the measles and anything that drips or spills on the deck, like sun tan lotion, grease, food, food condiments, etc leaves a stain that doesn’t wipe off.
What is composite decking? Composite decking is nothing more than compressed wood pulp (saw dust) which is usually mixed with recycled plastic to give it some stability.
How can it get so dirty? Mold needs an organic food source to survive and the wood pulp serves that purpose, so mold will grow on composite decking just as it would on a wood deck. If you have ever seen how cardboard absorbs a drip of oil, you will understand how composite decking absorbs spills, it goes in beneath the surface but still it is visible and that is what makes cleaning tough.
Sodium percarbonate based cleaners are highly effective because when mixed with water they create a bubbling action much like “alka-seltzer”™ and when applied to composite decking these bubbles will actually dissolve and lift any organic material to the surface which can be easily cleaned off.
Cleaning is simple, apply the mixture to the affected area of the deck, allow it 15 minutes to penetrate and to start breaking up the stains, while the area is still wet take a deck scrub brush and in circular motions scrub the spots out, when cleaning is complete rinse the area well with water. A pressure washer may be substituted for the scrub brush, but light pressure, max 1,000 psi, is all that is needed.
The key, when cleaning is to clean small sections at a time and always keep that area wet with the mixture while scrubbing, if the area dries before the cleaning is complete the organic matter could settle back below the surface and the process would have to begin again.
Sodium percarbonate is also a great product to use to prevent mold, simply apply a coat to your deck in the spring and fall and this will break up and dissolve any organic matter that is starting to make your deck it’ new home and food source.
Not all Sodium percarbonate based products are made of the same quality ingredients, strengths vary from 10 to 90% and there are additives necessary to take the sodium percarbonate mixture below the surface of the composite decking, without these additives the sodium percarbonate will only clean what sits on the top of the decking. The right formulation will be the difference in how clean your deck will come out.