This is how to build a Square Foot Garden Frame from 2x6s and 4×4 lumber. Mel Bartholomew, years ago, wrote the book Square Foot Garden and this frame is based on his 4 foot square design. Any wider and you can’t reach to the center. You can find info. all over the web on designs. This is how I did mine.
I made the sides from 2″x6″ common lumber 43 1/2″ long. End posts are 4″x4″s 9″ long. When I do it again I will use 2″x8″ lumber for the sides to get more depth. Then the 4x4s will be 3″ taller than the sides.
The posts are cut to a 30 degree angle for decoration. I used a table saw. You could use a mitre saw or even a circular saw with a cutting guide. Pre-cut the 4 posts and clamp them together for a stable surface, if you do it with a circular saw.
Using a Kreg Pocket Hole Jig I attached the sides. You could use dowels. Pocket hole screws were easiest. Since I didn’t used treated lumber, I don’t expect this frame to last forever. Using caulk, primer and paint will help it to last longer. I use thin strips of wood stapled together for the grid. You could just use string tacked to the sides.
The best thing I added was a trellis to the north side of the frame. I grow beans and peas on this. It is made from 1/2″ electrical conduit you can get at any home improvement store. You will need two 10 foot sticks of 1/2″ metal conduit, four conduit clips and 2 corners. You will also need trellis netting. The conduit was cut 60″ tall for the sides and 45 1/2″ for the top. It is best to cut and mount the sides loosely first and then measure the top length. There can be variations.
I have been using this frame for 4 years now. What I would do different. Make the sides with at least 2x8s instead of 2x6s. Deeper the better. Look around on the web on how to make the soil. I used some from a local fertilizer place and it was terrible. Locate the frame where it gets sun all day.