How to Build Raised Beds With Concrete Blocks

Build a raised bed and make a garden possible in areas without good soil or drainage. Bring gardening into reach for someone with a disability by raising the bed to a more accessible level. Concrete blocks make building a raised bed easy. The final result is attractive as well as sturdy. A concrete block raised bed will last for many seasons, yet it will be easy to remove, should the need arise.

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

• Concrete blocks
• Vertical supports (pipe sections, rebar, wood)
• Stakes and string
• Heavy work gloves
• Fine wire mesh
• Weed barrier cloth
• Planting soil
• Tools:
• Measuring tape
• Shovel
• Hoe
• Pick (optional, depending on soil conditions)

Planning a concrete block raised bed

1. Evaluate the area to be planted. Does it drain well or is the underlying substance clay or rock? How large will the planted area be? Will you build one large bed or several small ones?

2. Use stakes and string to mark the boundaries of the bed or beds. Will the entire growing area be within reach? If not, revamp the plan, making smaller beds and allowing for passage between them.

3. Dig out the existing sod or other growth. Remove everything down to below the roots of existing growth. Use a pick to remove rocks, if necessary.

4. Place a layer of weed barrier cloth in the dug-out area if there is a danger of weeds germinating beneath the bed. Lay fine wire mesh to discourage burrowing varmints.

Building the bed

5. Position the first layer of blocks around the perimeter, taking care to leave the cloth and/or wire undisturbed. Butt them snugly to each other, end to end, with the open sides facing up.

6. Place the second course of blocks, beginning at the center of one of the first layer blocks so the seams alternate. Continue with additional roads if needed. The finished pattern should resemble a brick wall rather than a checkerboard.

7. Brace the walls by pounding supports against the back of the interior openings, through all of the levels. This positioning will allow the weight of soil and crops to press the blocks against the braces, rather than away from them.

8. Place a layer of gravel in the bottom of the bed if drainage is an issue. Top with high quality growing soil (not just top soil). Water the bed thoroughly to allow the contents to settle.

Tips & Warnings

• The number of braces you need depends on several factors: the interlocking capabilities of the blocks, the height of the walls, the size (and therefore the weight) of the bed contents. Larger beds, higher walls and non-interlocking blocks will require a larger number of braces. Calculate the number of blocks needed by measuring the circumference of the bed and dividing by the length of the blocks. Allow for the wrapping at corners. This gives the number of blocks needed per layer. While traditional concrete blocks have large hollows, some of the more decorative styles feature narrow hollows for supports. Choose the braces according to the type of blocks used. Place the top row of bricks on their sides to provide seating along the top of the wall. Reduce the soil layer to the bottom of that row to avoid loss. Alternatively, place a layer of capping blocks to finish off the wall.
• Braces extending above the blocks can cause nasty injuries. Trim all braces for safety.

References

• Raised Bed Gardening; University of Missouri Extension Service
• Container Gardening for All; University of Missouri Extension Service
• 6 Strategies for Urban Vegetable Gardening; Megan O'Neill