Construction of a Self Wicking Garden Bed

Materials

• 8 pieces 1200 mm x 200 mm x 50 mm ACQ treated pine sleepers per frame
• a quantity of 100 mm treated pine self tapping screws
• 4 pieces of flat brackets (or whatever you call them)
• 1 piece of slightly larger than 1200 mm x 1200 mm square colorbond sheet metal
• a quantity of 15 mm button head self tapping screws
• 1 piece of builder's poly film (200um thick) measuring 1800 mm x 1800 mm
• 3 pieces of non woven polyester weed mat or frost mat 1800 mm x 1800 mm

The following are a sequence of shots showing how I built the raised bed..

The old vegetable plot

Digging out and levelling the base.

I needed to dig it out a bit so that the raised bed is not so high (on orders from she who must be obeyed). I then had to level it before I install the frames.

Frames installed with a colorbond base.

I attached the sleepers together with treated pine screws at each end directly to each other.

I then attached a colorbond sheet using button head screws and laid that color-side down. 

I then placed the frames on top of each other.

Securing the frames together

Laying the builders polyfilm for the reservoir.

Installing the overflow outlet

External view of the overflow pipe.

I secured the frames with each other using an l-shape bracket as seem. One bracket at each corner.

This seems sufficient to prevent the frames from shifting. Once soil is added, the additional weight will prevent any movement.

The next step (because I have a flat metal bottom), I directly laid the waterproof polyfilm