How to Build a Retaining Wall (Block), Step by Step

This is the build sequence for a segmental block wall up to about 4 ft. Past that, get it engineered.

1. Plan and check

Run your wall through the calculator first: confirm the base width, whether you need geogrid, and whether you need a permit.

2. Excavate the base trench

Dig a level trench the full base width plus 6 inches, deep enough to bury the first course (about 10% of wall height, minimum one full block) plus 6 inches for the leveling pad.

3. Build the leveling pad

Place and compact 6 inches of crushed stone, dead level. This single step decides whether your wall is straight for 30 years.

4. Set the base course

Lay the first row of block on the pad, level front-to-back and side-to-side, checking every block. Bury it. This is the most important course.

5. Stack, backfill and drain

Stack courses with the running-bond offset and the built-in setback (batter). As you go: place drain rock behind the blocks, run the perforated pipe at the base to daylight, and compact backfill in 6-8" lifts. Add geogrid layers where the calculator says.

6. Cap it

Glue the cap blocks on with concrete adhesive, finish grade so water runs *away* from the wall, and seed or mulch.

The calculator's materials list tells you how many blocks, how much stone and how much pipe to order.