I would like to build a box to store our cushions on the deck but concerned about potential mold issues due to high humidity if I make it waterproof. It does rain often here. My question is whether this is advisable. Would I just have some screening built into the box to allow for ventilation? Also any advise on materials used to build a box would be appreciated. I am thinking of using cedar boards along with some kind of plastic wrap to keep the rain, spiders and rodents out.