I am trying to devise a raised bed for my vegetable garden that won't leave my rented house with moisture problems in the roof and something that drains super well to endure the 6 month rainy season coming up here in Guatemala. I'm planning on building 8' long, 1'wide, 1' deep beds along supporting walls using a fine metal mesh stapled in as a bottom to allow maximum drainage. My only problem is I can't just let those wet troughs sit directly on the roof 24/7/365 without a moisture problem. I was considering setting the troughs on 9' by 14" pieces of heavy corregated tin roofing so that the water could flow under the troughs and yet the corregated design would support the mesh bottom and wieght of the dirt. What do you think? Does anyone have any better ideas? I'd love to hear them! thanks