I am building a 4'x 8' flower bed. The bed is 32" tall with a floor made out of 1x4" cedar four feet across. Soil depth is 12 inches, 32 cubic feet (8x4). Worst case 7.481 gallons per sq foot x 8 lbs of water per gallon = 60 lbs x 32 = 1915 lbs.
The design uses corrugated steel for the sides with two 2x4s screwed to the steel--one at 12" deep on the inside to support the 1x4 flooring and another 2x4 at 24" deep (the steel is 24" deep by 8'). On the outside there is a 1x4 frame with supports on the ends and at 24" intervals. So each side has two 2x4s and two 1x4 and corrugated steel, all eight feet long. The ends are the same with 4 foot lengths. Is this frame strong enough?