The compost bin for this project has three bays and a floor. The bin provides one bay for new waste, a second bay for compost that's in the process of breaking down and the third for finished compost that's ready to use in the garden. A raised floor in this compost bin allows air circulation underneath the pile, making the gas exchange that occurs during composting more efficient.
Measure two 2" x 6" boards for the outer floor supports of the compost bin to a length of 9 feet 3 inches. Each of the three bays will be 3' wide for a sum of 9 feet. The extra 3" will cover the depth of the two end joists. Use a circular saw to make the cuts while firmly holding the boards in place on two sawhorses. These two boards will be the front and back floor supports.
Now prepare the side pieces, also known as headers. Cut two 2" x 6" lumber 30" long. To get both pieces from one board, make the first 30-inch cut, and then re-measure and cut for the second piece.
Once the outer floor supports are cut to length, cut the center joist to a length of 9 feet. This will run parallel to the two outer boards and will attach to the headers. This center joist adds stability to the floor frame and will help support the load across the floor.
Next, cut six additional floor supports from the 2" x 6" stock to a length of 14-1/2" each. These six boards, two per bay, will strengthen the floor even more.