How thick does your retaining wall need to be?

When it comes to building your walls, no matter how simple it looks careful planning is extremely essential. A wall that wages a battle with gravity like a retaining wall must be planned carefully to withstand lateral earth pressure or retain any material (usual soil) and prevent it from sliding or eroding.

An ordinary person without knowledge in construction may actually fail to recognize that retaining walls are scattered almost everywhere. It can be seen primarily in parks, gardens, and public facilities. On many occasions, the ideal location for a retaining wall includes areas where a foundation's downhill side is under pressure from sliding soil. To know more about retaining walls, their ideal thickness, and how to build them correctly for them to last, here is a simple guide to get you started.

What is Earth Pressure?

Before anything else, it may be difficult to understand why there is a recommended thickness to retaining walls without knowing about earth pressure as it is a crucial concept to understand when discussing retaining walls. To put it simply, it is the pressure that the earth or soil exerts on the retaining wall. As a result of the surface's pressure, the wall tends to deflect outwards.

Earth pressure is further divided into active earth pressure and passive earth pressure. The activated earth pressure deflects the wall away from the backfill, whereas passive earth pressure exerts a force on the soil.

For a skilled engineer or construction expert to analyze a given wall design's overall stability and determine the lateral earth pressure, various soil factors must be known. Soil factors that are essential include:

  • Weight of a soil unit
  • Internal friction angle (for sands)
  • Indicators of cohesion and plasticity (for clays)
  • The location of the water table

The wall's stability is verified once the lateral earth pressures have been determined. This includes checking for soil-bearing capacity problems, wall overturning, and base sliding. Following the sizing of the wall, the strength of each wall member is assessed, and steel reinforcement is chosen.

How thick do retaining walls usually need to be?

Now that we know the pressure that our retaining walls need to accommodate, we can talk about wall thickness. The following are some general guidelines that designers use to determine the geometry of a wall

  • The breadth of the base is 1/2 to 1/3 of the wall's height.
  • 1/8 of the size of the wall, but no less than 12 inches thick.
  • For each foot of wall height, the thickness of the stem is 6 inches plus 14 inches.
  • The stem should be placed on the base so that 1/3 of the total base width extends forward from the stem's face.

What is the ideal thickness for a concrete retaining wall?

The required minimum reinforcement cover has an impact on wall dimensions (usually member thickness) in addition to basic structural requirements. This can increase the thickness of the wall by several inches, and it varies based on the severity of the exposure, the type of soil used, the reactivity of the earth, and other factors. For proper concrete installation, the top of the stem of anycast concrete retaining wall should not be less than 12 inches.

How high should a reinforced concrete retaining wall be?

The height of most retaining walls, whether load-bearing or not, is between 3 and 4 feet on average. As a general rule, every construction more than 4 feet tall should have some structural support built into it.

Backfill and Drainage

One area that is frequently overlooked, if not ignored, is the need to drain the backfill of precipitation and/or groundwater. Hydrostatic pressure can induce retaining wall failure or, at the very least, damage.

If there's heavy rain or other wet conditions, a retaining wall's ability to drain water is essential to its long-term stability. If the backfill is not adequately drained, it can get saturated, putting more strain on the wall and making it less resistant to sliding. Good drainage, quick compaction, and better sliding resistance are all advantages of granular backfill material.

How to build a concrete retaining wall

“Good buildings come from good people, and all problems are solved by good design.” – Stephen Gardiner

Retaining walls are vertical or near-vertical structures designed to retain material on one side, preventing it from collapsing or slipping or preventing erosion. They provide support to terrain where the soil’s angle of repose is exceeded and it would otherwise collapse into a more natural form. (1)

Like any other structure in construction, concrete retaining walls should be built with a precise engineering method. To create a concrete retaining wall, here is a glance at the usual installation process:

  1. Determine the size, shape, and area of the walls to create a design.
  2. Prepare the site for construction.
  3. Dig the foundations and lay them out.
  4. Create forms and place rebars when necessary to reinforce the structure.
  5. Fill in the gaps between the footings and the wall with concrete. Allow a few days for the concrete to dry.
  6. Every 4-6 feet, make contraction joints.
  7. Install drainage and waterproofing system after removing the forms.
  8. Finish the wall's surface according to your preference.


It may sound easy to build and install a retaining wall. However, for a retaining wall to last, you need to design it well while using the appropriate material for your project. Failure in retaining walls can lead to costly damage to property and injury or death.

If you want to have a retaining wall installed on your property, get in touch with our team.


  1. Retaining Walls | Designing Buildings

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