I'm responsible for a large greenhouse (30 x 20 x 12 feet or so) with lots of (movable) benches but no soil beds. The floor is concrete and the dwarf walls are breeze blocks on the inside and brick on the outside (so probably a cavity!)
What I thought of doing was building another dwarf wall parallel to a long side and filling the gap with soil/compost to make a lot more growing space. The likely size woud be about 20' long by 3' wide and as deep as I have soil for - probably about 2'. If it works I could replicate it on the other side.
Is this a good idea? The two pitfalls I can forsee are overloading the concrete base and adequate drainage. Any ideas?