We almost doubled the space we had by adding two new beds to our square foot garden. The front one will be for squash and the middle for sweet potatoes.  We saved huge on this project by re-using wood. Most of this wood was from the deck I had replaced ten years ago. I ended up never getting around to burning it. So it has been in the very back of the yard for years. We have gradually pulled out and used most of it!  Total cost is $7.00 for the box of screws!