My composite deck that was built 12 years ago was showing more mold each year. I tried many different products that I think usually contained some bleach but after a few months the deck looked just as bad or worse than before.I decided to try Corte Clean and so ordered the 3 pack Corte Clean. We applied it as directed including using a brush to do a more thorough job. After the 1st application the deck looked some better but still not what we expected it to be. So the next day we applied it again and this time it cleared up the mold completely. I plan to use it again next spring.