How to Build a Landscape Wall and Keep It in Tip-Top Shape

Landscape walls are a gardener's way to fight gravity: They're typically used to hold back part of a yard that would otherwise lead to a landslide. They can also step up an especially steep slope, cut down on erosion, and carve out distinct outdoor rooms at different elevations.

But in order to do their job—and stay stable—landscape walls must be correctly constructed and maintained. That includes building a solid base, adding enough tilt to the back (called battering), and including drains to keep water from damming up behind them. With the soil constantly pushing on retaining walls, they need regular maintenance and occasional repairs. Here's how to build yours and keep it in the best shape possible.

How to Build a Landscape Wall

Dig a Trench and Add Sand

Start by creating a path for your landscape wall using wood stakes and a mason's line, then dig away excess soil. (The first course, or line, of the block will need to nest in a trench, sitting at least 2 inches below the soil in front.) Line the back face and inside of the trench with landscape fabric, then add a 1-inch-deep layer of sand for bedding.

Install Drainage

To ensure good drainage, install a perforated drainpipe behind the first course of the landscape wall, using soil to create grading and a slight incline. Make sure to fit the open ends of the pipe run with grate inserts to prevent clogging. Pull the landscape fabric down to cover the drainage pipe, then add a 3-inch layer of crushed rock.

Lay Down the First Line

Set the first base block into the sand and tamp with a mallet. The blocks should tilt back slightly, creating a slight incline and forcing the wall to lean into the hill. Nestle the remaining base blocks into the sand; align them along the top and back surfaces, checking with a straightedge and tamping each block with a mallet. Complete the block pattern until you have a flat first course; apply cap units with construction adhesive, cut away excess landscape fabric, and backfill the hillside behind the wall. At the front of the wall, add fill dirt to cover at least half of the base course blocks.

Choose Landscaping Wisely

Is planting on top of a retaining wall safe? Yes—as long as you choose your greenery wisely. Plants will help integrate the wall into the landscape, but you have to select species that won't disrupt the structure with their roots. Plant flowers and groundcovers closest to the wall, while placing small shrubs at least 3 feet away. Large shrubs and small trees should be at least 6 feet from the wall and large trees at least 15 feet.

The Most Common Problems for Landscaping Walls

The Problem: Improper Drainage

Improper drainage is a major culprit behind retaining-wall failure. Why? If water isn't being diverted, moisture and waterlogged soil build up behind the wall, compromising its integrity. Correctly installing piping is critical to the success of your landscape wall.

Even if your piping is doing its job, you still need to maintain it. Some walls include weep holes along the base, allowing water to run through the structure. Regularly clean these openings with a piece of wire or a screwdriver to ensure they stay open. If there is a drainpipe behind your wall, check during the rainy months that the pipe isn't plugged.

The Problem: Tilted Walls

If a landscape wall is leaning downhill instead of tilting back slightly, you know it's losing the battle with gravity, succumbing to the weight of the earth behind it. The same holds true if a section of the wall is bowing. Unfortunately, landscape walls can't be simply pushed back into proper alignment; they must be torn down and rebuilt.

The Problem: Loose Bricks or Rocks

Saturated soil can cause your retaining wall to shift, breaking loose its bricks or rocks. Cracks may also form if the wall wasn't built correctly or the mortar wasn't prepared with the right consistency.

First, address any underlying drainage issues or structural problems. Then tackle the loose material. If it's a brick in a mortared wall that's breaking free, remove it and chip away the old mortar around it. Apply a layer of ready-mix mortar, available at home supply stores, to the bottom and ends of the brick, then slide the brick back into the opening. Add mortar to the top of the brick by pushing mortar from your trowel into the space with a jointing tool or the back of an old spoon. Scrape the excess mortar from the brick with a trowel, then wipe the brick clean with a wet rag. Repair loose rocks in a mortared stone landscape wall in the same manner.

If it's a cap rock on a stone wall that's loose, chip off the old mortar, then set the cap rock in a new bed of mortar. Fill any gaps around the cap rock with mortar.