How to Cut and Install Retaining Wall Topper Stones

Topper stones make a wall look finished but have to be cut to fit a curved wall.

How do I add square topper stones to a curved retaining wall? And how do I attach the topper stones so that they don’t get knocked off? -Paul

Those wedge-shaped stackable stones are great for building curved retaining walls, but once complete it leaves you with unsightly gaps. For a finished look, you can add topper stones, but it poses some challenges since:

• • Topper stones are usually square, not wedge-shaped, so if you want a smooth top you’ll need to cut them to fit the curve. If your curve is very gradual, you might be able to get away with spreading out the small gaps so they aren’t noticeable.

• Topper stones are also a bit wider and lighter than the wall blocks, so it’s easy to kick them out of place or bump them with a lawn mower. I have topper stones on my wall, and I’m always knocking them loose and having to put them back.

Instead of my kick-and-replace method, there are better ways of finishing off your retaining wall! Try these tips.

Use a Masonry Saw

Retaining wall blocks can be cut using a masonry chisel and mallet, but for the topper stones you may want to spring for a diamond blade masonry saw. Similar to a wet tile saw, masonry saws make very clean, straight cuts that will give a nice finishing touch to your wall. Masonry saws can be rented at your local rental center – all you’ll need is an extension cord and a garden hose to provide lubricating water.

The bottom stones will be cut along the lines, and the top one will be left square.

How to Measure the Cut

If you enjoy geometry, you can cut each stone at an angle to curve along your wall. For a faster job that looks just as neat, try this approach:

• • Step 1: At the beginning of your wall, place stones #1 and #3 in their places. You’re going to be cutting both of these.

• • Step 2: Lay stone #2 on top of them, with the front corners lined up. You’re NOT going to be cutting this stone, you’re just using it as a cutting pattern.

• • Step 3: Draw lines on stones #1 and #3 where the top stone overlaps them.

• • Step 4: Cut stones #1 and #3 along your lines.

• • Step 5: Replace the stones on the wall, and now stone #2 should fit neatly between them.

• Step 6: Now put stone #4 on top of stones #3 and #5, and repeat. The odd-numbered stones will be cut on both edges, and the even-numbered stones will be left uncut.

The back view shows the overlap of the stones and the cutting line being marked.

Adhere the Stones

Once your topper stones are cut and fit, you can keep them in place using masonry adhesive. Masonry adhesive usually comes in a tube for use with a caulk gun and should be available at your home improvement store. Examples include:

• Titebond Landscape Retaining Wall Adhesive
• Quikrete Polyurethane Construction Adhesive
• SRW Retaining Wall & Paver Adhesive

For a very solid wall, you can also use the adhesive to attach the stackable blocks themselves.

Further Information

• Retaining Walls (Video)
• Types of Retaining Walls for Your Yard (video)
• How to Build a Stackable Block Retaining Wall (article)
• How to Build Retaining Wall Corners (article)
• How to Align Blocks in a Curved Retaining Wall (article)