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Sixteen cast concrete sections were used to build this 4’x12′ by 1′ deep raised bed.  The fence wire used on each side of the raised bed is hinged horizontally, 4 feet above the concrete, to provide access.  A one foot square grid (3 independent 4’x4′ sections are added to experiment with Mel Bartholomew’s Square Foot Gardening method.  The combination of PVC pipe and fence wire sitting on the raised bed was added to keep chickens and other animals out of the bed, but could also be used as framework for a greenhouse.

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 Constructing the form

A wooden form was made from 2×4 and a 2×6. Same volume as one $5.00 80 lb bag of Sakrete.

Screws are used to assemble/disassemble the form, allowing removal of the finished product.

One 4 foot piece of 3/8” rebar is placed in the concrete when the form is half full of concrete.

The form is setup for using short sections of ½” diameter PEK pipe at each end and in the middle. PEK is removed after the concrete is removed from the form, leaving 2 holes in the concrete where short pieces of rebar can be inserted vertically to lock the concrete sections together.  The hole in the center of the concrete can be used to help stabilize a trellis.

As an extra, since the wood form has a joint on one surface, a short piece of vinyl flashing is put into the form before pouring to prevent forming a ridge in the finished product.

The form can be removed after 24 hours, but 48 hours would be better.  Concrete takes many days to reach almost full strength.  The concrete sections can be used to construct the raised bed immediately after removing the form if it is handled gently and not dropped or stressed.

(Click on images to enlarge.)

Concrete Form RB

 

Another method using concrete blocks: