10 Steps To Building the Perfect Concrete Retaining Wall

Concrete retaining walls are ideal for residential and commercial landscaping projects. While there are different materials for building retaining walls, most property owners prefer concrete retaining walls because they’re strong, durable, weather-resistant, and versatile.

A sturdy concrete retaining wall holds back tons of soil, preventing it from sliding and damaging your surrounding landscape. The wall helps increase the space of your yard when building a patio, garden bed, pathway, pool, or any other feature on your property.

However, if not installed properly, a concrete retaining wall may end up tilting, cracking, or bowing. Such a wall may collapse and damage your beautiful landscape. This guide takes you through concrete retaining wall detail so you can build a secure wall on your property.

Poured Concrete or Concrete Block Retaining Wall?

When building a concrete retaining wall, you may wonder whether to go for the poured or concrete block retaining walls.

Poured concrete walls are stronger and easier to waterproof than blocks. However, poured concrete wall installation can be tricky, and it takes longer to complete the project. You’ll need to hire a skilled concrete contractor to do the job.

On the other hand, a concrete block retaining wall is relatively stronger and easier to install.

Tools and Supplies Needed

Whether you choose a poured concrete or concrete block, here are the tools and supplies you may need:

  • Concrete blocks
  • Concrete mix
  • Capping blocks
  • mortar
  • shovel
  • Pick
  • Chalk line
  • Garden stakes
  • Wheelbarrow
  • Mason’s string
  • Gravel
  • 3/4-inch pipe
  • 4-inch perforated drain pipe
  • Metal rebar
  • Metal reinforcement strips
  • Level
  • Trowel
  • Hand tamper
  • Sand
  • Screed board

After assembling all the equipment, you need to learn how to build a concrete retaining wall in detail.

Steps To Installing a Concrete Retaining Wall in Detail

This is how to build a 4’ retaining wall in detail:

Step 1: Plan

Your concrete retaining wall detail should start with a plan.

Before everything else, determine the shape, height, and length you need for your retaining wall. Contact your local council to know the recommended retaining wall height and obtain a permit.

Generally, any retaining wall above 5 feet high requires a permit. However, if you’re building a 4’ retaining wall or less on your property, you don’t have to worry about permits.

You may need to consider barriers such as root systems and drainage pipes you’re likely to encounter during excavation. If there are nearby trees, shrubs, or pipes, you should plan how to cut or relocate them.

Step 2: Mark the Site

Using a chalk line, garden stakes, and string, mark the lines where excavation will take place. Ensure the lines are straight or parallel depending on the shape you want for your wall.

A line level can help you mark parallel lines that will serve as reference points during excavation.

Step 3: Excavate

Use a pick and shovel to excavate the area marked with garden stakes and string for the foundation. Ensure you create a flat-bottomed trench where you’ll pour your concrete foundation. The trench should be at least 8 to 12 inches deep and 24 to 28 inches wide.

The goal is to create a compatible base material for laying your blocks. Remove extra soil to make at least 12 inches of the clear area behind where you’ll install the retaining wall. The clear area behind your wall will hold moisture barriers, gravel, or any ideal drainage feature.

Step 4: Prepare the Footing

Pour concrete mix into the trench to create a footing where you’ll lay the first course. Ensure the footing is about 4 to 6 inches high to remain slightly below the grade. The concrete foundation should remain hidden after completing the project.

Compact the concrete mix with a hand tamper and level the top of your concrete foundation using a towel. Allow the foundation to dry or heal before laying the first course. 

Alternatively, you can use sand if you don’t want to wait longer for the foundation to heal. Use a screed board or hand trowel to level the sand.

Step 5: Lay the First Course

If you’re using a poured foundation, use a chalk line to mark an outline on the surface of the foundation. Pour a layer of mortar inside the outline and ensure it’s at least 1-inch thick.

Lay the first concrete blocks on the foundation mortar. Position your concrete blocks vertically using a level. Use stakes and masonry string to create a straight row of concrete blocks.

Step 6: Place the Perforated Drain pipe

Install your perforated drainpipe at least 4 to 6 inches behind the first course. This pipe will keep water away from the concrete wall. 

Ensure to place the pipe before backfilling with gravel. Add gravel on top of the perforated drainpipe.

Step 7: Install Subsequent Courses

Apply a layer of mortar atop the first course and spread it on each block. Lay the second course of blocks atop the battered blocks. To strengthen your wall, place the blocks in a half-bond manner. You can also fill the blocks with gravel for extra strength.

When laying the second course, insert the 3/4-inch pipe or weep holes into the mortar. Install subsequent courses until you reach the required height. 

Use a mason’s string and level to ensure each course is straight and level. Scrap the excess mortar on the face of your blocks using a trowel.

Step 8: Reinforce the Wall

Lay metal reinforcement strips into the mortar to reinforce the horizontal joints after every second or third course. 

For vertical reinforcement, insert metal rebar into the hollows to strengthen the rows.

Step 9: Lay Capping Blocks

Apply a layer of mortar atop the last course of blocks and lay metal reinforcement strips. Lay your capping blocks on top of the mortar to cover the wall. 

Add mortar between the capping blocks and use a hand trowel to smoothen the face of the blocks.

Final Step: Backfill

Remember to backfill with gravel when adding subsequent courses. A great option is to add soil on top of the gravel and place a sod. Alternatively, you can add crushed concrete to the soil as a drainage material.

Final Thoughts

You now have a concrete retaining wall detail for your landscaping project. However, if installing a concrete retaining wall sounds daunting and intimidating, hire a skilled concrete contractor to help you with the job. Your contractor should provide drawings and structural calculations and advise you on the need for permits.

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