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.
Get the first course right
Sweep before stacking
Provide plenty of drainage
Step up after two full courses are below grade
Which blocks are best?
Make smooth cuts with a saw
Mark cuts with a soapstone pencil
Keep space between tiers
Keep the joints tight
Backfill with stone
Keep the capstones even
Tall walls need engineering