How to Build Retaining Wall Corners

How do you construct 90° angle corners when building a stackable block retaining wall? -Adolfo

Constructing corners can be tricky when building retaining walls, since some types of blocks aren’t square and may not be textured on all sides. That’s why it’s important to consider your corners and curves carefully when choosing the type of block to buy for your retaining wall.

Some types of blocks come with corner units that make the job easy, and others are finished on all sides so the corners can be exposed. When choosing and buying blocks, make sure you have the accessories and instructions for whatever corners, curves, or special circumstances you have in your plan.

Here are some tips for tackling corners in your retaining wall project.

Retaining Wall Corners Using One-Sided Blocks

The most common blocks for retaining walls are textured only on one side, with a lip at the back that butts up against the row under it. They’re often wedge-shaped to allow for turns and curves. This type of block is designed more for curves than sharp corners, since only one side of the block is meant to show.

To construct retaining wall corners using wedge-shaped blocks:

• Outside Corners: Most retaining wall outside corners built with wedge-shaped blocks are curved, rather than a 90° angle, since it’s impossible to make an outside corner without showing the cut (and unattractive) end of the blocks. Wedge-shaped blocks are easily laid in a curve, or you can cut the sides of rectangular blocks to achieve the same curved effect.
• Inside Corners: It’s easier to construct 90° angle inside corners with wedge-shaped blocks, since the backs and sides of the blocks won’t show. Start the first row in the corner, then overlap the joints in each additional row of blocks, cutting any odd sized blocks to fit.

Retaining Wall Corners Using Corner Units

If you’re using stackable blocks that are only textured on one side, the best solution is to choose a block system that comes with corner units. The corner units are finished on two sides and connect to the adjoining blocks to form a 90° angle.

Each system is designed differently, so each type of corner unit will have slightly different installation instructions. In general, you’ll start at the corner and work your way out, beginning with a corner block that alternates facing right and left on each row.

Retaining Wall Corners Using Multisided Blocks

If your retaining wall blocks are rectangular and finished on at least two sides (like many pavers and cinder blocks), you can easily stack them to create a corner. Alternate the pattern to divide the load and keep the corner from splitting, and be sure to use some masonry adhesive to hold the corner pieces in place:

Further Information

• Retaining Walls (video)
• Types of Retaining Walls for Your Yard (video)
• How to Build a Stackable Block Retaining Wall (article)
• How to Align Blocks in a Curved Retaining Wall (article)
• How to Cut and Install Retaining Wall Topper Stones (article)
• How to Build a Retaining Wall with an Outside 90° Wall (wonderhowto.com)
• How to Build a Retaining Wall with an Inside 90° Wall (wonderhowto.com)

Retaining wall systems and corner installations:

• Retaining Walls (Ferrell Builder’s Supply)
• Retaining Walls (North Idaho Masonry & Hardscape Center)