How To Build A Retaining Wall That Will Last For Years (Step-By-Step)
Time: 6-12 Hours
Anyone with a strong back can stack blocks high enough to make a retaining wall, but creating one that will last for years takes proper planning and execution.
That's because your wall will endure environmental forces from mother nature on a daily basis.
Rain water, wind, and gravity are just a few of the forces you'll be fighting against.
Not to worry, our guide will go over everything you need to know to build a retaining wall that will last for years.
Equipment / Tools Needed:
- We recommend using a walk behind trencher to break down the soil before digging
- Pavers or concrete blocks
- Brick chisel
- Rubber mallet
- Wooden stakes, string and a line level
- Sharp gravel
- Vibratory plate compactor
- Work gloves
- A gravel rake
- A corrugated drainage pipe and pipe sleeve
- Concrete adhesive and a caulking gun
Before you get started, you're going to want to measure out how wide your trench will be.
For a successful retaining wall your trench is going to need to be wide, deep and level. The trench needs to be deep enough for at least one full layer of initial course to prevent tipping when the ground freezes.
We recommend laying out the blocks and then measuring off at least an additional 8 inches or so behind the material which will show you exactly how wide your trench needs to be. A standard concrete block is 8 inches wide, meaning your trench should be at least 16 inches wide if you're using concrete blocks.
Digging and Leveling The Trench
At this point, you should know exactly how wide and long your trench is going to need to be. Before you start digging, we recommend using a trencher to break up the soil to save yourself some back pain.
Here in Asheville, NC we have carolina clay which can be absolutely miserable to dig through.
We almost always trench before we do any major digging. Make sure you don't trench too deep that you may disturb too much dirt beyond your required depth. You'll eventually be using a plate compactor to compress the soil but don't over-trench your soil to prevent too much work.
To reiterate, you'll need to dig deep enough that your first row of stones will be almost completely covered.
Once the trench is dug, you'll need to level out the area.
Start by using your gravel rake and shovel to remove any unnecessary soil.
Place your level on the soil across the full length of your dig and adjust areas accordingly. You may also want to lay your initial layer of material and re-measure.
Compacting Your Soil
After everything is nice and flat, you're going to need to compact the soil. The reason this is important is that your trencher, shovel and other excavation tools may have disturbed the soil.
Disturbed soil can cause settling which can absolutely wreck your work thus far.
Fire up your vibratory plate compactor and begin compacting the soil.
Filling The Trench
Now that your trench is complete you can begin filling with gravel or crushed stone. If you're using crust stoned we recommend .5 or .75 inch stone diameter to handle the elements most efficiently.
Credit: familyhandyman.com - Skid Loader Dumping Crushed Stone
Ensure that your crush stone goes no higher than .5 inches higher than your final first layer.
Placing The First Course
When placing your first course of stones, you're going to want to stay as close to the center of the trench as possible.
Use a long, 4-6 ft torpedo level to keep each block level and even.
Set the blocks with a rubber mallet according to your level.
Credit: familyhandyman.com - Setting blocks level with a rubber mallet
Your first layer is by far your most important. If this is not level and set correctly, your entire retaining wall could be ruined.
With that in mind, take several passes with your mallet and level looking for any inconsistencies.
Prepping Your First Course Of Blocks
Using a metal wire brush scrape the top of your blocks.
You're going to want to really scrub with your wire brush, removing any small debris to make sure that there is nothing that will keep your following layers from sitting flat.
Placing and Aligning Your Full Second Course
After your first course is set and prepped you'll want to line up your second course. Thank you to Family Handy Man for this great graphic on what proper alignment should be for your second set of blocks.
Basically, you want the end of your second course to go over about 50% of it's width, sitting on top of your excess loose stone.
Similar to your first course take your torpedo level and rubber mallet and set the blocks until they are completely flat across. Make sure you're looking across several blocks at a time to avoid any slants.
Once things are level use your wire brush to clean off any dust and debris from the blocks to prevent any misalignment.
Repeat this process until your retaining wall is at least as high as the slope above the retaining wall.
Where needed, measure and rough cut your blocks to the appropriate length.
Backfill Your Retaining Wall With Gravel Or Crushed Stone
If you've done everything right up to this point you should have about 6-8 inches behind your stone wall.
Once your wall is high enough, you can begin backfilling this area with stone behind the retaining wall. Use a gravel rake to flatten or slope off the back-filled stone.
Congratulations! At this point you have a completed retaining wall.
As always, if you have any equipment rental needs in the Asheville area we're happy to help!