Poured Concrete Raised Garden Beds – Precast Form Build PART 2

Pipes and Wire

animation of parts for the concrete raised garden beds forms
Pipes and Wire are cast into the panels

While this is drying (or soaking in) I’ll cut the plastic pipe to length.

cutting plastic pipe with a miter saw
Plastic conduit cut to length. A hacksaw would work just fine for this

I use wire wrapped around the pipes to add strength to the ends where the concrete is the thinnest.

galvanized wire wrapped around plastic pipes
Galvanized wire “springs” are made by wrapping them loosely around a pipe

I wrap wire around a pipe like a spring. Then open it up a bit.

wire grid added to wet concrete for reinforcement
Concrete reinforcement grid is cut with bolt cutters

With small bolt cutters I cut a section of stiff wire mesh to reinforce the center section of the panel. This will be laid in the concrete as it’s poured.

Final Assembly

Now assemble the forms with the wire and pipes. I add some latex calking to make the forms water tight and to add a small fillet in the corners.

adding latex caulking to make molds water tight
Latex caulking added to gaps and corners

This takes only a few minutes per form. This also fills any small gaps where the sides, ends, and base meet.
Latex works well as it’s not overly strong and will allow you to disassemble the mold easily once the concrete sets up. Don’t use regular silicone for this. It’s too strong and will be difficult to remove later. Latex caulk is all that’s needed.

apply latex caulk to seal the concrete forms
Add caulking when Ends are first attached to the base

I realized later that it’s easier to add the caulking to the ends before the pipe is in place.


I set the forms over sawhorses and level them in both directions.

levelling forms with a 24\" spirit level
Forms are levelled

I cover the wire and pipes with a cloth and spray the form with vegetable non-stick cooking spray.

adding latex caulking to make molds water tight
Cloth covers pipe and wire
spray the concrete raised garden bed forms with cooking oil
Cooking Spray works as a non-petroleum release agent

I’m going to use a crack resistant concrete mix that has fibres added for more strength. It’s only a few dollars more per bag so why not?

bags of quickrete concrete mix with added fiber
Concrete mix with fibres

Some have suggested that fibre reinforced concrete would be strong enough so wire would not be needed. But adding the wire gives me an extra bit of insurance that doesn’t cost much in time or materials. So I’m sticking with it for these castings.

mixing concrete by hand with shovel and wheelbarrow
Mix concrete in a wheel barrow

I mix the concrete in a wheel barrow and shovel it into the form filling it half way.

filling the form with wet concrete mix
Shovel wet concrete into form

I use a wooden mallet to settle the concrete and bring bubbles to the surface.

using a reciprocating saw without the blade to vibrate the concrete
Vibrate the forms with a power tool

You can use the edge of an orbital sander or a reciprocating saw without a blade to vibrate the forms and settle the concrete.

filling the form with wet concrete mix
Wire mesh piece added then topping up form with more concrete

I lay in the wire mesh then top up the form with more concrete. I’ll let this set up for a bit then come back with a corner tool to round over the edges on the sides.

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