How to Construct a Concrete Masonry Unit (CMU) Garden Bed

To construct a Concrete Photo of several CMU garden beds at the UCCS GreenhouseMasonry Unit (CMU) Garden Bed,  you start by leveling off a plot of land with string.  By placing four stakes in the ground to make a rectangle of your choice as shown in the figure at the right.Figure showing a rectangle with four stakes marking the corners to illustrate how to setup a CMU bed. The figure also has two red lines, criss-crossed across the center to illustrate how to level-off a plot of land with string.

As shown by the red arrows you can measure the length of the diagonals with a tape measure. If they are the same the same distance apart you can assume that your lines are perpendicular to each other.

After confirming that you have staked out a rectangle you can now determine what height you would like your beds to be.  For reference our height was 18 inches or the equivalent of two blocks high.  At the lowest of the four corners measure from the ground up to your bed height.  From the low corner tie and level a string line to the other two corners at the height you just measured, and from those two corners tie and Photo demonstrating string-leveling of a CMU garden bedlevel a string level to the last corner forming a rectangle.(Like above)

 From there you can place blocks using the sting lines as guidelines to check square and straightness of the bed. Another thing to note is to stager the joints of the bed wall otherwise your bed walls will just fall over.  For beds like ours I typically layout the first layer using the strings lines and a level then I fill in the holes in the center of the block with dirt. Then I layout hardware cloth across the first layer and cut and fold it into the bed by making diagonal cuts at the corners.  Then I place the top layer, stake it down with rebar and fill the beds and the top blocks with soil.  Note: Each terrain is different and you may need to adjust the last steps to place the bed as your grade changes.  Also you can stake off multiple beds if they are the same width and length and are in line with each other.

 

Climate Battery Garden Bed System

This group of pictures shows the creation of specialty beds we have constructed for growing crops  in the greenhouse in winter without using the heater.

The bed system utilizes a climate battery which is constructed out of two layers of stacked concrete block (CMU). A perforated pipe manifold (image A) is placed on top of sheet insulation, and is then encased in gravel (images B and C).  Next, a third layer of block is placed around the bed and the entire bed is filled in with soil  (image C).  The inside manifold comes out the wall end of each of the 12' x 4' beds and two beds are joined together and share a fan (image C). 

Each winter day, solar heating of the greenhouse will rise to the peak and will be driven into the climate battery. Each night this collected heat will radiate into the soil, warming it beneath the plants (image D).


Image A: piping is placed inside the beds

Image B: gravel is used to encase
the piping

Image C: gravel is raked across
the piping

Image C: finished beds, filled with soil

Image D: the finished beds inside the Greenhouse