How to Build Concrete-Block Raised Planting Beds
Create ideal growing conditions and easy-on-the-back gardening
Raised beds make it easy to amend poor soil and garden at a back-friendly height. Here's how landscape contractor Byron Moffett built these with hollow concrete blocks.
1. To prevent cracks in the masonry over time or as soil shifts, excavate to pour a footing 8 inches wide and 6 inches deep around the entire 4-by-8-foot perimeter. Fill the trench halfway with concrete. Lay down two pieces of ½-inch rebar in the center of the trench along the footing's four walls. Fill with concrete.
2. Once the footing cures, set one L-shaped corner block in a ½-inch-thick bed of mortar. Working around the perimeter, set one course of the 4-by-8-by-16-inch blocks in mortar, spacing them a half-inch apart and leveling them as you go. Repeat, alternating the orientation of the L block for the second course so that vertical joints don't line up.
3. With two courses in place, strengthen the walls by placing a 15-inch length of rebar in each corner and filling the voids in the blocks with concrete (each block has two hollows separated by a divider). Repeat in every other cavity in the block walls.
4. Top with smooth capstones 2 inches thick; mortar in place, leaving a 2-inch overhang to create a comfortable perch for tending beds—or just hanging out.