I have a rather large deck and boat dock that I recently resurfaced with TimberTech. The deck is in redwood T&G with the railing kit, and the dock is in the 5/4″ cedar planks. They both turned out great. However, they both started to show black mold after about 4-6 months. I think a lot of reason for the mold is that I live in Missouri which has high humidity and the house is surrounded by trees. Mold and mildew is a constant problem on anything outside. After searching for a cleaner, I found Corte Clean on the Internet and gave it a try. It did a great job on cleaning the surface areas and was very easy to use. The railing was a little more of a challenge as it tended to leave a milky residue if it wasn’t completed washed off. I ended up using a power washer for the final rinsing. I found Corte Clean to exceed my expectations.