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How Much Does a Retaining Wall Cost?

A retaining wall is more than just another decorative element or another landscaping feature. These walls serve an important function: to prevent ground from slipping and sliding. Though decorative in nature, retaining walls are a must for some areas. Homes that sit several feet above the street and lawns that hover near the edge of a sidewalk often need a concrete block or brick wall that holds the ground in place and keeps the ground from shifting and falling. While many homeowners only care about how much it will cost to install a retaining wall, they also need to look at the construction and components of those walls.

Cost of Retaining Wall

  • Wood retaining walls: $15 per square foot
  • Natural stone retaining walls: $25 or more per square foot
  • Interlocking concrete retaining walls: $20 per square foot

Uses of Retaining Walls

A retaining wall is essentially a solid wall that covers a patch of dirt. Made from brick, concrete or stone pavers, the walls are strong enough to support the dirt and keep the ground from shifting. Some homeowners use retaining walls when landscaping or building an outdoor garden or flower bed. Shorter walls arranged in a rectangular fashion or another shape create a raised flower bed that homeowners can use when gardening. Many homeowners use smaller retaining walls as landscaping elements to differentiate between different types of plants and to create a focal point for their lawns.

Installing A Retaining Wall

Before installing the pavers or stones used in the wall, it's important to properly slope the area. The ground underneath the stones should have a slight slope that keeps water from pooling up behind or under the stones. This slope helps water drain away from the area. Without the right slope, the water can saturate the ground and increase the weight of the dirt enough that it pushes the retaining wall down.

The next step involves digging a trench for the stones. This trench should be slightly wider than the stones, and contractors will add a thin layer of sand or another fill material to the trench. Tampering the ground and ensuring that the space is level are other important steps. The builder will then place a layer of pavers on top of the sand, check that the stones remain level and add more sand if required. Contractors will add additional sand as needed as they build up the retaining wall. They also use sand or another material to fill in any gaps between the pavers after making the wall as high as desired.

Interlocking Stones

Those looking to save money on the project might opt for interlocking stones instead of individual pavers. These stones resemble steps with a bottom stone attached to an offset top stone. The pieces all fit together like a children's block set, making it easy to build a retaining wall. Builders will still need to dig a trench and pack down a layer of sand first, but they can easily connect the blocks together to form the wall. Most builders use a heavy hamper to tamper down the stones, and they'll add a small amount of water at the end. This lets them track the drainage and ensure that the wall drains properly.

Types of Retaining Walls

There are several different types of retaining walls that homeowners can choose from when picking a design. These designs include:

  • Gravity walls
  • Cantilever retaining walls
  • Sheet pile retaining walls
  • Anchored retaining walls
  • Counterfort retaining walls

Gravity walls feature a thinner top and a wider bottom and lean against a surface while cantilever walls feature a wide and thick base with an even wall that can support greater weight. Sheet pile retaining walls use thick pieces of metal or wood inserted into the dirt, and most people don't know that the walls are even there. Homeowners can also choose anchored retaining walls or counterfort retaining walls if they need additional support.

Disadvantages of Retaining Walls

Retaining walls aren't a one size fits all solution to shifting ground problems. While a small wall with a few layers of stones can securely hold a garden in place, that same wall won't support a mound of dirt that sits on the edge of a property. The taller the wall, the less support that it offers. For taller walls, homeowners need to opt for cables placed inside the wall, or they need to choose shorter walls that are wider in size. 

Retaining walls can also shift over time, especially when not properly installed. As the dirt and ground behind the wall shifts, it puts pressure on the wall. This will eventually cause the top of the wall to shift away from the bottom and can cause the entire wall to topple. Improper drainage can lead to the foundation of the wall pushing away from the ground creating additional troubles. Other potential problems include damage from termites and other insects in wood retaining walls and cracks and chips in brick, stone or concrete retaining walls.

Retaining Wall Costs

The cost of a retaining wall depends on the material chosen, the overall height of the wall and the length of the wall. Wood retaining walls start at $15 per square foot, while concrete retaining walls start at $20 per square foot. Homeowners interested in using natural stone will find that those stones increase the cost to $25 or more per square foot. 

In addition to the materials used, the job also requires excavating the ground and removing any dirt or surface materials from the space. This can add a few thousand dollars to the job, depending on the length of the wall. Though experts generally recommend that retaining walls sit no higher than four feet without any additional support, it's possible to have a retaining wall of up to 10 feet high. These taller walls can cost nearly $20,000 while a six-foot-wall can cost around $13,000. Decorative retaining walls and those that serve no real purpose generally cost less.

Last updated on Jan 26, 2016

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