We replaced our pine deck with a "maintenance free" TimberTech deck because we were sick of the upkeep. To our chagrin we realized after a couple of years even these types of decks require annual maintenance to look their best. Regular cleaners and scrubbing wouldn't remove the blackish spots so we did an on-line search for cleaners and found Corte Ckean was recommended for TimberTech. We found it at a local hardware store and tried it. One small bag easily cleans our approximately 15x21-foot deck. After thoroughly sweeping, hosing and overnight drying, we apply Corte Clean the next morning with a pump sprayer in full sun. Stubborn spots require a light scrubbing and re-application of the cleaning solution. After a morning of work the deck looks like new again! Local stores stopped carrying it so we're grateful to be able to order on-line. If it weren't for this product we probably would have replaced the deck with a patio by now!