The Allan Block Blog: How do I build retaining wall corners?

Written by: Ryan Miller

Corners are almost always more time consuming, typically cost more money and are generally more difficult to build. We always recommend incorporating a radius whenever possible, but when you must install a corner, here are a few general recommendations to follow.

Inside corners are easily constructed using standard Allan Block units. By removing part of the lip with a chisel or saw, the blocks can be overlapped for a strong interlock. If your retaining wall needs reinforcement, follow the instructions for adding grid to corners.

Using your saw or chisel, remove the raised lip from one block, and 1/3 from the left side of another. Set them in place at the beginning of the base course.
Locate the adjoining retaining wall so that the raised lip on the modified block is lined up with the raised lips on the opposite retaining wall. Finish installing the entire base course in both directions.
Modify two more blocks, this time remove the raised lip from one block, and the right third from another. Use these blocks to start the second course.
Continue the process to the top of the retaining wall, alternating as you go.

Outside corners take more time and skill, but AB Corner Blocks are all you need to make an outside corner. Always build your retaining walls by starting at the corners and working out. AB Corner Blocks are manufactured with a 12° (Ref) setback. With some minor adjustments, the blocks can work with any setback. See AB Tech Sheet #298 (Using the One Piece AB Corner Block) for more details.

Set the first corner block in place and install the two perpendicular base courses. Level, backfill and compact.
Place an alternating corner block on the second course and set the entire second course of block in both directions. Level, backfill and compact again.
Repeat as often as needed to the top of the retaining wall.

When you are done with the inside and/or outside corner, place your caps on: