Build a Long-Lasting Block Retaining Wall
Anyone with a strong back can stack up a bunch of blocks and build a pretty retaining wall. But it takes skill and planning to construct an attractive wall that can also handle immense pressure, shrug off the forces of gravity, stand for decades and laugh in the face of Mother Nature.
That’s the kind of wall we wanted to learn how to build, so we went to work with some hardworking hardscaping pros. They showed us that it’s all about a solid base, proper drainage and the right materials for the job. They also shared a few handy tips they’ve picked up over the years.
Make the trench wide, deep and level
Size the trench so there’s enough room for the block and at least 8 in. of space behind it. Excavate deep enough to completely bury at least one full course, including space for 6 to 8 in. of base material.
Establish a level trench to ensure an even layer of base material. That will help prevent the wall from tipping after freeze/thaw cycles. Our experts use a laser level and a story pole to determine the depth of the trench.
Compact the trench
Lay a crushed stone base
Our experts prefer crushed stone for the base rather than naturally occurring gravel dug from a pit. Crushed stone is a little more expensive. However, it provides better drainage, and because of the sharper angles on the stone, it requires less compacting, and once it’s compacted, it stays that way.
Joe and Jake have found that crushed stone sized between 1/2 in. and 3/4 in. is best suited to handle the heaving forces created by the harsh freeze/thaw cycles here in Minnesota. Avoid rounded stones like pea gravel or river rock; they don’t form strong interlocking bonds like angular stone.
Leave the stone no more than 1/2 in. higher than you want the final height to be, and then make a couple passes with a hand tamper or plate compactor. You’ll notice the stone is almost 100 percent compacted as soon as it’s laid in the trench. The same type of stone will be used for backfilling, which also eliminates the need for hauling in multiple materials.