Ok, we have an Amish made "ark" roughly 20'x20'x12ft high. It's for our kids to play on. We live in Florida and it is outside but in a shady area. Over the years it had gotten very dirty with lots of mildew on the surfaces. I spent 5 hrs pressure washing it and it looks nearly new but I would like to coat it to preserve some finish and hold off the mildew. Have read the whole forum on deck maintenance but still dont have a good idea what might be best to use. The pressure wash opened up the wood grain in some ares as I had to get quite close to the wood in several areas to get the dirt and mildew off. Any suggestion s would be greatly appreciated. Thanks.