Landscaping ideas to make your yard look more lush and dramatic abound, but here’s one project you might want to ponder if your house sits on a hill or slope: building a retaining wall.
Retaining walls not only add visual interest—defining garden spaces or other topographical features—they perform a critical function as well. On property that isn’t level, heavy rains can wash soil down to the lower points of your yard, resulting in a muddy mess and smothering the plants below. A retaining wall helps hold all that back.
If you think your yard could benefit from a retaining wall, here are the steps on how to make that happen.
What you’ll need
- Shovel
- Work gloves
- Level
- Paving stones
- Tamper
- Retaining wall blocks
- Landscape adhesive
- Landscape fabric
- Soil for fill
Step No. 1: Figure out where your wall should go
The placement of a retaining wall depends on your yard, but it usually comes down to a balance between aesthetics and functionality, says Danny Lipford, a home improvement expert and host of “Today’s Homeowner,” a TV and radio show.
Typically, it makes sense to place a retaining wall at the lowest point of where your property slopes. However, if you’re suffering serious erosion on a large incline, you might want to consult with an engineer. Retaining walls 4 feet or higher usually require a permit from local building authorities.
Once you decide where you want your wall to go, insert stakes into the ground at each end of the wall, one at each corner (so, four stakes total—or more if your wall has right angles or curves). Then connect these stakes with string so you can picture how the wall will look. You can also measure the dimensions to figure out how many blocks you’ll need.
Blocks manufactured specifically for retaining walls are available at home improvement stores, and are a good idea since their uniform shape makes them easy to stack. They also have a self-aligning rear lip (see photo) that comes in handy, as you’ll learn below.
Materials and sizes for blocks can vary, so you’ll have to measure the length of your wall to get an idea of how many you’ll need per row.
Let’s say the style of block you choose measures 1 foot long and your wall is 20 feet long; each row will need 20 blocks. Next, settle on how high you want your wall. If your blocks are 4 inches high, a 3-foot wall will need nine rows with 20 blocks—or 180 blocks total.
Step No. 2: Dig out a trench
A retaining wall needs a level, solid foundation, says Lipford. Dig out a trench about 6 inches below ground along the perimeter of where your wall will be (be sure to save this soil to put back in later). Level the soil at the bottom of the trench as you go along.
Step No. 3: Add a stone base
Add 2 to 3 inches of crushed rock—what’s known as paver base—to your trench. The rock adds stability and strength to the foundation. Then use a nifty tool known as a tamper to push down the rocks and compact the base, says Lipford. (This step can get dusty, so you might want to wet the paver base lightly with a hose before you tamp.)
You’ll want your first row of blocks to be half-buried under the existing soil level, so if your blocks are 4 inches tall, make sure to leave a 2-inch gap between your crushed paver base and ground level, or 3 inches for 6-inch-tall blocks, and so on.
Step No. 4: Stack your blocks
Lay your first row of blocks (each row is known as a “course”).
When you start to build up your retaining wall, stack your rocks at a gradual incline toward the slope, rather than straight up. The slope should generally be 1 inch in for every foot high. This incline counteracts the pressure of earth on the other side.
“If you stack your stones straight on top of one another, you compromise the strength of the retaining wall and it will be more likely to fall over time,” says Tonya Bruin, CEO of To Do Done Handyman Services.
One way to strengthen your wall is to get manufactured blocks with an interlocking lip in the back; these blocks allow you to easily stack each block over the bottom layer to automatically create an incline; the lip also adds extra oomph against the pressure of the dirt from the other side.
The block’s manufacturer will provide a pattern for how to lay the blocks, but the rule of thumb is you want to stagger the joints, like below, which also increases your wall’s strength.
As you put down each layer, clean off the top. For added stability, Lipford advises applying landscape adhesive between the rows of blocks. Your final blocks will be the more decorative “cap” blocks.
Step 5: Add landscaping fabric then backfill with dirt
Before you fill in the back of your retaining wall with soil, add a layer of landscape fabric along the backside of your bricks to keep soil from leaking through cracks. Once it’s in place, cut the fabric to just below where the top of your soil will be. Fill the rest of this trench with soil and compact lightly with a tamper to avoid settling later. Add plants if desired.
