In this how-to video, TOH Senior Technical Editor Mark Powers shows how to make a concrete block garden border that does double duty as extra backyard seating.
1. Lay out the width and shape of the wall. Place a stone at each end of the run, then drive a stake at least 1 inch around the sides of the stone to mark the width of the trench.
2. Tie a level mason's line between the stakes—to use as a measuring guide when digging the trench. Hook the string in a notch on each stake to make it easier to move the line out of the way as you dig.
3. Dig until you get past the dark topsoil and reach the lighter subsoil, but no less than 6 inches. Measure off the mason's line to keep the bottom of the trench level. If your ground slopes at all the trench will be deeper at some points than others.
4. Line the trench with paver base—a mix of crushed stone and stone dust. Tamp it down in 3-inch layers.
5. Fill the trench until the shallowest part of it is still deep enough to fit half the height of one block, plus one inch.
6. Spread an inch of stone dust over the paver base.
7. Set the first stone at the shallowest point of the trench. Check it for level side to side, front to back, and corner to corner. Tap the stone with a rubber mallet to set it.
8. Lay the next stone by butting it against the first and dropping it straight down. Set each stone this way, checking it for level and tapping it in place.
9. When the first course is done, backfill the extra space around the stones with stone dust and dirt.
10. Stagger the joints, starting the second course with a half block.
11. Score the block with a mason's chisel, then make a thin channel in the score line.
12. Split the stone with the chisel and clean the edges with the claw end of a brick hammer.
13. Lay a bead of masonry construction adhesive along the first course, and lay the second course of blocks.
14. Continue to stagger the joints as you lay two more courses, or until your wall is 18 inches high, gluing at least every other course. Cap the wall by gluing down blocks turned perpendicular.
15. Let the adhesive cure for a day.