How to Build a Retaining Wall on a Slope

A retaining wall integrated into a sloping front lawn adds polish and curbside appeal. A retaining wall constructed on a sloping backyard or back garden brings a beautiful landscaping touch to the house by allowing you to create more living space while holding off soil erosion.

How to build a retaining wall on a slope depends a lot on the location where you plan to build, the lay of the land, and the materials you want to use.

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Consult a Professional

Before you start building your retaining wall, it would be best to get a consultation. You can talk to a registered landscape architect or engineer to help you plan out the project. Do not forget to check with your local authorities for building codes and building permits.

Walls up to 4 feet in height do not require permits. However, there might be some utility pipes running underground that you need to avoid when you start to dig. If you are planning to do the project yourself, it would be best to also check with your doctor just to make sure you’re fit to finish off the job.

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Get Organized

Here is a list of some of the necessary materials needed you will need to build your retaining wall:

  • Stakes
  • Long continuous string
  • Shovels: long handled flat shovel, round pointed shovel, trenching shovel
  • Tamper tool
  • Tarpaulin sheet
  • Torpedo level
  • Rubber mallet
  • Grit sand
  • Crushed gravel
  • Concrete blocks
  • Cap blocks
  • Construction adhesive
  • Draining mechanism
  • Gloves
  • Safety helmet and shoes

Here are the basic steps on how to build a retaining wall on a slope.

1. Start Digging

Dig into the earth to span about 2 feet back from the front side of your planned wall. Bore in stakes and tie strings firmly across to establish the desired wall height. Dig 6 inches deeper at the base. This trench should be deep enough for you to bury the base block. Start digging at the lowest point of the slope.

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2. Level the Base

Add about 3-6 inches of stone or crushed gravel into the trench. Compact it with a tamper tool. Then lay in 1-2 inches of grit sand. Thin this layer with two passes on a tamper tool.

Make sure that you the base layers are level using the torpedo level. It is important to level the base so that laying the other blocks to build the wall will not be difficult.

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3. Lay the Base Blocks

Put on the base blocks one at a time. Pound each block with a rubber mallet to set the blocks. Check each block for plumb (or level) with the torpedo level. Adjust each block’s plumb with additional base material underneath, if necessary.

Laying the base block and making sure each base block is level is the most critical part of the project. Strength and stability of the retaining wall are dependent on the support blocks.

When the base blocks are entirely laid in, fill the gap behind the blocks with the sand and gravel aggregate. This will provide strength reinforcement and provide proper drainage.

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4. Build the Wall

The second layer of the blocks should start with a half block. Build the wall to the desired height. Use the recommended construction adhesive throughout the layers intermittently. Be mindful when laying the blocks with adhesives so that costly mistakes are avoided.

Remember that you need to check if your blocks are plumb with your torpedo level. For these following levels, it is best to put the torpedo level across two adjacent blocks. Adjust the blocks where needed.

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5. Backfill and Put in Drainage

With every layer of block added, you have to backfill the gap at the back of the trench with sand and gravel aggregate. Tamp the added backfill.

Midpoint through the layering of the wall, put in your desired drainage mechanism to allow water to flow and empty out beyond the wall. Allowing water to drain beyond the wall will relieve pressure and ensure the integrity of the retaining wall.

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6. Finish with Capstones

Put capstones as the last layer to put a finished look to the retaining wall. This is not required, but it will give off a polished style to your retaining wall.

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When to Call an Expert

Talk to a licensed architect or engineer at the planning stage to guide you on how to build a retaining wall on a slope. They can provide you with the design, engineering, and advise on the scope of work this kind of project will entail.

Retaining walls can be built from various materials like wood, stone, and concrete. Heights can vary from a small 3-foot wall to a tall 12-footer. Drainage mechanisms and techniques vary depending on the wall to be built.

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If your property has a steep hill or a gentle slope, building a retaining wall is a project you should consider undertaking. The retaining wall will prevent soil erosion. It can also create additional pleasant living spaces in otherwise unused areas of your property.

Were we able to make you think of building that retaining wall on your slope? Drop us a comment to let us know or share this article with a friend.