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The Best Way How To Build A Retaining Wall In 7 Steps

Landscaping with retaining walls and flowerbeds in residential house backyard

A retaining wall is a great way to create a level area in your yard and provide extra seating for outdoor entertaining. Retaining walls provide a good way to prevent soil erosion on steep slopes. But before you can enjoy the benefits of your new wall, you need to build it! Here’s a step-by-step guide to help you get the job done.

How To Build A Retaining Wall

1. Choosing The Right Retaining Wall Material

When choosing a material for your retaining wall, you’ll need to consider several things, including cost, durability, appearance, and ease of installation. Concrete blocks, brick, natural stones, and timber are all popular choices with their own pros and cons.

Do you want a cantilever retaining wall or a concrete retaining wall? Narrowing down your retaining wall ideas will help determine the best course for your particular retaining wall.

Ultimately, the best material for your retaining wall will be the one that meets both your practical needs and your aesthetic preferences for retaining walls.

2. Measuring The Slope Of Your Land

There are two types of slopes: profile and cross-sectional. The profile slope is the slope of the land as viewed from the side, while the cross-sectional slope is the slope of the land as viewed from above. It’s important to measure both types of slopes when you’re building a retaining wall. 

  1. To measure the profile slope, you’ll need a level and a tape measure.
  2. Find two points on the ground that are level with each other
  3. Measure the distance between those two points with the tape measure
  4. Use the level to see how much higher or lower one point is than the other. This will give you your profile slope measurement

To measure the cross-sectional slope, you’ll need a transit or level and a tape measure.

  1. Find two points on the ground that are level with each other
  2. Use the transit or level to sight along an imaginary line between those two points
  3. Measure the distance between those two points with the tape measure, and then multiply that number by 100. This will give you your cross-sectional slope measurement

3. Marking The Layout

Buried plastic natural gas line in hole of yard. Shovel in soil and yellow buried gas warning flag marking location.

First, call 811. They’ll send a technician out to mark the location of any underground power lines, gas lines, or water lines. 

Then, measure the area where you will be building the retaining wall. Use stakes and string to mark out the perimeter of the retaining wall. Be sure to keep the string taunt so that your line is straight.

Once you have your perimeter marked, use a spirit level to ensure your retaining wall will be level. If it isn’t, adjust your stakes until it is.

Lastly, mark where your footing will go with spray paint. This will ensure that your footing is level with the ground and not too deep.

Now you are ready to begin digging! 

4. Digging The Trench For Your Retaining Wall

Use a shovel or excavator to excavate the trench. The trench should be about twice as wide as the retaining wall itself. So if your retaining wall is going to be two feet wide, dig a four-foot-wide trench. Make sure the sides of the trench are perfectly straight by using a string line or mason’s line and level.

As for depth, most retaining walls need to be at least 18 inches deep for them to be stable. However, if your soil is sandy or loose, you may need to dig your trench even deeper.

5. Building The Base Of Your Retaining Wall

Once you’ve excavated the trench to the desired depth, it’s time to line it with gravel. This step is crucial because it helps with drainage and prevents erosion. The gravel also provides a stable foundation for your retaining wall.

Once you’ve lined the trench with gravel, tamp it down. You can also install landscape fabric to prevent weeds from poking through the base.

Install a perforated drainpipe on one side near the bottom of the excavation. The pipe should slope down from front to back at a rate of 1/8 inch per foot. 

You’ll need to add some sand to the base before you can begin laying your first course of bricks or wall blocks. The sand will help level out any uneven spots in the base and provide a stable foundation for your retaining wall. Use a rake to spread an even layer of sand over the entire base. Then, use a plate compactor or hand tamper to compact it and create mechanically stabilized earth that will help prevent soil erosion.

Now you’re ready to start building your retaining wall.

6. Stacking And Leveling The Wall Blocks For Your Retaining Wall

Two men maneuvering large concrete blocks into place with the aid of a crane visible in the background.

Adjusting For Slopes

To do this, you will need to excavate the ground behind the proposed retaining wall to accommodate the first row of wall blocks. The top of the excavation should be level with the ground in front of the retaining wall. Next, fill the hole with gravel and compact it with a hand tamper. 

Leveling As You Go

As you lay each subsequent course of block, leveling is key to ensuring your retaining wall is stable. To level the wall blocks, use a mason’s line stretched between wood stakes driven into the ground at both ends of the retaining wall. The line should be set at the desired height of the course being laid. As you lay the blocks, check them against the mason’s line frequently to ensure they’re level. 

Laying Rows Of Blocks

Begin by laying the first course of blocks along the foundation. Be sure to level each block as you go. Once the first course is in place, start working on the second course.

For stability’s sake, it’s important to stagger the joints in each successive course so that they don’t line up perfectly with the joints in the course beneath it. You can also install pins or rods through the cores of adjacent blocks at regular intervals.

Adding Landscape Fabric For Drainage

A deep trench filled with stone gravel.

Begin by measuring the length and height of the retaining wall you’ll be building. Once you have those dimensions, add an extra 2 feet to both the length and the height. This will give you plenty of fabric to work with as you build your retaining wall.

Cut your landscape fabric to size using scissors or a utility knife. If you’re using a utility knife, lay down a cutting board or piece of scrap wood first to avoid damaging your floor or table surface.

To install the fabric, you’ll need to excavate a trench at least 12 inches wide and 12 inches deep behind the retaining wall.

Once the trench has been excavated, lay the fabric in the trench and make sure that it’s level. If there are any irregularities in the fabric, they’ll need smoothing out.

Begin attaching the fabric to the first course, or layer, of blocks using construction staples. Space the staples about 12 inches apart, driving them in at an angle so they’re flush with the blocks. Continue until the entire first course is attached.

Repeat this process for each subsequent course until the retaining wall is complete. Be sure to smooth out any wrinkles in the fabric so that everything lies flat against the blocks.

Backfill the trench using gravel and tamp it down flat, but don’t overpack it, or you may hurt the integrity of your retaining wall. Once you have about 2 inches left until the trench is full, add soil and tamp it until it’s even with the ground.

Once your retaining wall is finished, trim away any excess fabric using scissors or a utility knife. You can dispose of this material in your household trash bin. Landscape fabric is not biodegradable, so it can’t be composted.

7. Finishing Your Retaining Wall

Add the capstones to your finished wall. The capstones make up the top layer of your retaining wall and will give it a finished look. Be sure to use mortar when adding the capstones to adhere properly.

Plant grass seed, sod, or plants. This will help give the area a finished look you can enjoy.

Farrell Lawn & Garden Center Can Build Your Retaining Wall

You can use a retaining wall to bring many benefits to any outdoor living space you create, but not everyone has the time or energy to install their own retaining wall. Farrell Lawn & Garden Center can help you get closer to having the outdoor area of your dreams!

Fill out our contact form today and get one step closer to your dreamscape.