lightweight materials for square foot gardening
I'm new to the forum. About 2 years ago I moved to Portland OR, from Salt Lake City Utah where I had built and mainted a couple of great square foot gardens.
We just moved into a new house as as much as I love the house, the backyard is small and largely shady. The other day, my partner had a great idea - GREEN ROOF. We have a mostly flat unattached garage at our house and with a few adjustments, and my building a good sturdy ladder, I'll be able to build a small green roof.
However, with that, I dont' want to actually plant onto my roof, I want to build the raised bed version of 4X4 garden and put them up on low stilts. Buildwise, it's not major - however, the weight is a concern. Does anyone know where I can source lightweight materials or kits to build the 4x4 bedframes? I would use the same kind as i would on the ground, I just don't want them to be made of wood as I think that's heavier.
Any info you guys can share would be great. I will post pictures as I get things going.