How to Build a Sturdy Retaining Wall That Will Last a Lifetime

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Compact the Trench

Compact the soil in the trench bottom with a hand tamper or vibrating plate compactor. This step is often neglected. The excavator, and even hand shovels, can disturb and loosen the top inch or two of soil, and that’s enough to make your wall settle—settling is bad!

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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 inch and 3/4 inch 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 inch 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.

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Get the First Course Right

Use a torpedo level to level each block front to back and either a 4-foot or 6-foot level to keep each course level and even. Set the blocks with a heavy rubber or plastic mallet. Getting the first course flat and level is extremely important, so take your time. Try to lay the course as close to the center of the trench as possible.

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