We tried all of the DIY solutions, pressure washing, and scrubbing with Dawn. Literally nothing worked. We were always left with little pockets of mildew and green algae on our white Adirondacks, fences and stone walkways. I asked the attendants at Chatham Bars Inn and The Breakers and they used the method. - Spray 30 second clean on the surfaces and let sit for 3 mins. - Hose off with a strong hose nozzle and wipe down with a wet cloth to get in the crevices. Note: If you’re starting out with a really dirty area, you’ll have to go through this process a couple times. LTKChathamBarsInn LTKNewEngland LTK30SECONDSSpray LTKHome LTKFindsUnder100 LTKSeasonal