Although most dimensions tend to be 4x8', Fred recommends building a garden box that is 3x6' for the simple reason that two to three feet is the arm span of the average adult. Anything larger can be more work and more difficult to maintain. This design is also much easier to transport.
Building a garden box might sound daunting to those who aren’t exactly carpenters, but don’t be afraid! It’s actually very simple and once it’s built, it will last you for many years to come. If you don’t have power tools of your own, ask a neighbor or friend.
For the base, you will need enough 2x8' untreated lumber for a 3x6' bed. This means buying at least three boards, and having them cut to the sizes you will need. (Two 6-foot long sides, and two 3-foot long sides.)
The corners are extremely important, not only aesthetically, so your box has nice, even lines, but functionally. You want your box to last a long time.
The corners are nailed together with three, 3-inch deck screws. The wood will expand and loosen over time from weather and wear, so the next step is to cover it with sturdy, corner brackets made of galvanized roof flashing. Fred cuts these from a large sheet, into four 6-inch corners. Secure these onto the corners with three truss screws on each side.
The Screen Frame (Side Panels)
For the side panels you will need wood for the 3x6' frame and some sort of mesh or hardware cloth. The mesh side panels are an important component to your garden box. These function as additional protection for your plants from animals, harsh weather conditions, or even your neighbor’s incoming Frisbee or stray ball. Fred recommends that it be at least 2 feet in height. The dimensions will be the same as your base, so that it sits perfectly on top.
There are several options for your screen material. The first option is regular window or door screen. This excludes ALL insects. And we mean all, including beneficial pollinators like bees and butterflies.
If you simply want to keep out animals or backyard chickens, just use chicken wire. Be aware, this does not keep out any insects, including pests!
And finally, the third option is hardware cloth. Fred recommends spending using a ½ inch or ¼ inch hardware cloth. This allows bees to enter and leave, but keeps out pests like the cabbage worm and cabbage butterfly.
Optional: The Shade Cloth Covering
You can further protect your bed from the elements by making a shade cloth covering. Fred recommends buying a 7x6' sheet of a 30-40% shade cloth. The percentage correlates to how much of the sun rays are being blocked.
You will also need two 1'x2'x7' lumber pieces to weight down each side of your covering.