How to Plan a Landscape Retaining Wall for A Yard

A good place to start planning is the local city hall.

Traditionally, retaining walls have been considered practical solutions for landscape issues such as erosion or loose soils. While these are necessary uses of retaining walls, it’s time to think more expansively about the possibilities.

Retaining walls can also be used for many value-added and aesthetically pleasing landscape features. Think about using retaining walls to create planting beds, multi-use spaces, sitting walls, or transitions to sidewalks. Retaining walls can carve out areas for patios, change steep slopes into terraces, or add beautiful landscape features to outdoor surroundings.

Know the Property

A good place to start planning is the local city hall. They can provide a scaled property map, which can be helpful during the planning and designing process and show property lines. It’s also advisable to contact local utility companies to understand where water, sewer, gas, and electrical lines may be buried on the property.

Consider Grade Changes

Once one has acquired a scaled map of the property from city hall, a useful tactic for designing retaining walls is to start at the lowest point and mark all grade changes in increments of one foot on the property map. This type of topographical map will help understand the property's various elevations and grade changes and help determine the wall's height.

Depending on the slopes and grade changes on the property, a retaining wall will be one of two different types:

Cut Sites: Retaining walls that are built directly into an existing slope. Require excavating the soil of the slope before the wall is built.

Fill Sites: Built on an existing slope. Require additional fill behind the wall as the wall is built.

Consult with a professional for any slope that is greater than 3 to 1 (i.e., 3 feet over, 1 foot down). If the retaining wall is over six feet high or if there is a slope below the retaining wall, consult with a professional before beginning the project.

Examine The Soil

Another factor to consider is the type of soil on the property. Granular soils are generally better for this type of project than clay soils. Heavy clay soils may require reinforcement.

To determine whether a soil is granular soil or clay soil, pick up a handful and squeeze it. Granular and sandy soils will not form a ball when squeezed; clay soils will. Also, never use organic soil to fill around a retaining wall. When squeezed in the hand, organic soil will form a ball and then fall apart.

If the soils surrounding and underneath the area where the retaining wall is to be built are of poor quality, they should be removed and replaced with higher-quality soils. Although replacing soils will add to the overall cost of a retaining wall, poor-quality soils take longer to compact and, over time, can cause issues with the integrity of the retaining wall.

Determine Surcharges

Another factor determining the type of retaining wall to build is what is uphill from the site. Added pressure uphill from the wall, such as driveways, patios, or pools, are known as “surcharges.” If the surcharges add enough pressure to the retaining wall, the wall may require reinforcement. The amount of reinforcement needed will determine whether a wall is a Gravity Retaining Wall or a Reinforcement Retaining Wall.

Reinforcement Retaining Walls require reinforcement, typically using geogrid.

Gravity Retaining Walls do not require reinforcement and can hold the soil behind them with their weight.

The degree to which the retaining wall leans back into the soil behind it is called the “set back” and is another factor determining whether a Reinforcement Retaining Wall or a Gravity Retaining Wall is required.

Think About Access

One final consideration is access to where the retaining wall will be built. Some sections of some properties may be difficult to access, especially with excavating equipment or building materials.

Retaining walls are for more than just practical. They can add value and beauty to the landscape. Take these five considerations into account while planning a retaining wall project.

Epic Lawns LLC provides top-quality lawn care and landscaping installation and maintenance to property owners in St. Charles, St. Louis, and Lincoln Counties. Call Epic Lawns at (636) 445-0824.