Retaining Walls

Sleeper Retaining Wall

A sleeper retaining wall adds a rustic charm to your landscape by using railroad ties, known as sleepers in the UK and Australia, or other forms of timber to shape the topography of your property. A sleeper retaining wall is an affordable, easy to install alternative to stone or poured concrete retaining structures. A well designed sleeper wall lends natural beauty to your property, makes drainage more efficient and prevents the topsoil erosion that can endanger the health of your plants.

Building your own retaining wall vs. hiring a retaining wall professional requires a knowledge of the essential functional features of these structures. A retainer must incorporate a form of drainage, so that water that accumulates in the soil behind the wall can escape. In stone gravity walls, this drainage mechanism is built into the construction of the wall itself, as water can escape through the cracks between the rocks. In a sleeper retaining wall, a drainage feature must be integrated into the construction of your project. In addition, any sleeper must be sturdy and tall enough to bear the weight of the slope.

Using Timber in Your Landscape

Wood is an organic material that gives your landscape a casual, unaffected aesthetic appeal. However, untreated timber is prone to moisture damage, rot, mold and destruction by termites and other insects. The timber used in a sleeper retaining wall must be pressure treated or chemically treated to prevent these hazards, or the retaining structure may be unstable.

A sleeper wall isn't necessarily constructed using railroad ties. As an alternative to treated timber or railroad ties, you can use redwood or other types of wood that are naturally resistant to pests and weather damage. Ancient redwood trees, which have held up to moisture and insect damage for thousands of years, have proven the resilience of this species.

Pressure treated, dimensional lumber provides a sturdy retaining structure that can withstand rain, snow, thaws or insects. To reinforce the structure against water damage, the planks may be assembled in such a way that they are not directly exposed to the earth or to moisture. Many homeowners are hesitant to use railroad ties in a sleeper retaining wall because a railroad sleeper may be treated with creosote, or coal tar, a chemical that can harm the environment if it seeps into the soil or water supply.

If a sleeper is thoroughly cleaned before being used in a retaining capacity, the danger of environmental harm from creosote is reduced. However, removing the creosote from a railroad tie may reduce the lumber's resistance to water. Although railroad ties offer a unique, weathered look that adds character to your landscape, the safest approach may be to use pressure treated dimensional lumber that hasn't been exposed to creosote.

Designing a Sleeper Retainer

A sleeper retaining wall may assume a number of shapes, sizes and functions. A basic sleeper retaining wall that's less than 3 or 4 feet tall may not require a permit from your local planning agency. A taller retainer, which requires more complex reinforcement and must usually bear a larger vertical weight load, requires a permit in many communities. If your retaining structure is a large scale project and your retainer must hold back a significant mass of earth, contact a local landscaping contractor to discuss local codes and structural requirements.

The design of a sleeper retaining wall should reflect the overall style of your landscape as well as its intended function. A low, simple structure can create an elevated space for a planting bed, while a taller, more complex structure may be terraced, with multiple levels for planting. Any design must incorporate certain basic elements, including a trench, anchors, backfill material and a drainage tile, in order for the project to fulfill its fundamental purpose.

With a standard timber retainer, a trench must be excavated at the base of the slope to hold the foundation timbers. A horizontal anchor is typically put in place behind the wall for extra reinforcement. A geosynthetic landscaping mesh may be used at the base to retain soil and support the timber structure. Gravel or another backfill material is used to allow water filtration, and a drainage tile is put in place for adequate water drainage. Though the structural components and design of retainer walls can vary, the essential elements are the same.

Adding a sleeper retaining wall to your property can be a simple, affordable way to enhance your topography, add visual interest and expand your planting space. When you work with a qualified, licensed contractor, you can feel confident that the project will be completed to your specifications and in accordance with local codes. Take the time to consult several trusted local contractors to find a professional whose experience and reputation for efficiency meet your needs.

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