The top of my deck railing is composite wood and hadn't been cleaned in 2 years. I scrubbed it down with plain water two days ago and let it dry. This morning I sprayed on a coating of Cleaner,let it set briefly, sprayed on another coat and took the scrub brush to it. Then I sprayed on another coat and brushed it again. After about 20 minutes (it was still wet) I rinsed it off with the hose. Not everything came off but it looks 100% better. This didn't work as well as I had hoped but the rail was in bad shape. I wouldn't want to do the entire deck floor like this. Overall, I'm satisfied.