Different Types of Retaining Walls and Their Purposes
The inside of your home is beautiful. It says “you” in every way and in every room. What about the yard around your house? Are you tired of looking at poorly designed yards without a hint of beauty? Retaining walls can attract attention to specific features in your yard and offer practical and aesthetic benefits to your landscaping.
Showcase beautiful stonework throughout your yard and prevent erosion at the same time. Need materials for a new retaining wall? Contact Batchelder & Collins for the answer to your masonry needs.
The Purpose of a Retaining Wall
A retaining wall is a structure designed to hold back soil or withstand land pressure. It is a structure that is designed to retain the shape of a landscape, hence its name. Lateral earth pressure that requires a retaining wall could be from backfill, soil pressure, soil erosion, liquid pressure, and even sand. Any sort of granular materials behind the retaining structure can cause this pressure.
When Did We Start Seeing Retaining Walls
The first retaining walls appeared as far back in history as ancient Egypt. At the time, they were an important part of Egyptian civil engineering, used to harness the power of the Nile to irrigate farming valleys and prevent soil erosion. Gabion-style retaining walls were the prominent form at the time, made from reeds that grew along the riverbanks. They would divert the flowing waters of the Nile into reservoirs and fields to improve farming conditions.
The interesting thing about retaining walls is that despite significant advancements in geotechnical engineering, construction methods, and building materials, retaining wall design and use have not changed much. They are still used to hold back land, create space, divert water, and prevent soil erosion.
What Are the Most Common Types of Retaining Walls?
There are four basic types of retaining wall systems:
- Gravity retaining walls
- Anchored retaining walls
- Cantilevered retaining walls
- Sheet pile retaining walls
Each has its own applications in landscaping and engineering. The type of retaining wall required for specific jobs depends on the material retention needed on site, the type of gravity to counteract, overturning and bending moments, shear forces, and the general conditions surrounding the wall.
Gravity Retaining Wall
Gravity retaining walls use their weight to resist lateral earth pressure. These types of walls are typically massive. This is because they require a great deal of gravity load to counteract the soil behind them. They must account for bearing, sliding, and overturning forces and may be constructed from a variety of materials, from precast concrete to concrete blocks to stone or masonry. They are suitable for heights of up to 10 feet.
Anchored Retaining Wall
Anchored retaining walls are used in areas of limited space where a thin wall is needed. They are especially suited for retaining loose soil over rocks. They can be built to great wall heights because of their means of construction, which utilizes deep wires or cable rods driven horizontally into the earth with the ends filled with poured concrete to provide the requisite anchoring. These anchors, also called tiebacks, serve to counteract sliding pressure and overturning.
Cantilevered Retaining Wall
Cantilevered retaining walls are composed of two elements: a stem and a base slab, both of which are constructed from precast concrete, prestress concrete, or reinforced concrete wall, which when the back is submerged under the retained material, form an L-shaped structure. These are the most common type of retaining walls in existence. They can be constructed on-site (cast-in-place) or precast offsite.
The base slab consists of a heel, which is situated beneath the backfill, and the toe, which supports the rest of the wall. These walls must consider various types of gravity, including bearing, sliding, and overturning pressure. They can be built to a height of 33 feet effectively.
Sheet Pile Retaining Walls
Sheet pile retaining walls are a form of pile wall that uses sheet instead of concrete. Most pile walls are constructed by driving reinforced concrete piles in a row deep enough to counter any forces attempting to push them over, then fronted with steel sheets. They can be temporary or permanent and offer high rigidity for retention of lateral pressure to extreme depths while avoiding any risk to surrounding structures.
Sheet pile retaining walls use the same principle as concrete pile walls but use steel sheets driven into a slope or excavated to a required depth. They cannot withstand the same pressure that concrete pile walls can and are only economical to a height of 20 feet.
Different Types of Retaining Walls
Though the types above are the most common retaining walls, many other types exist. These include gabion, counterfort or buttressed, MSE, crib, and hybrid walls.
Gabion Retaining Walls
Gabion retaining walls are built of rectangular wire mesh boxes filled with rock or other materials, then stacked in “cells.” They are most commonly used to stabilize steep slopes and can often be seen along the sides of highways holding back cliffsides to prevent landslides or falling rocks.
Counterfort or Buttressed Retaining Walls
Counterfort retaining walls, also called buttressed retaining walls, are a form of reinforced retaining wall which begins with a cantilever structure that is then supported with monolithic counterforts diagonally against the front of the wall and base slab to provide extra strength against gravity. These walls are generally built to heights between 25 and 40 feet.
Mechanically Stabilized Earth Walls (MSE Walls)
MSE retaining walls are among the most economical types of retaining wall and make use of metallic strips or plastic mesh run through granular material to create reinforced soil. This reinforced soil provides extra stability for the concrete block, panel, or temporary earth wall that holds the rear gravity in place.
Crib Retaining Walls
Crib walls are a type of gravity wall constructed of boxes of pre-cast concrete or timber, which then interlock together. These boxes can be filled with granular materials like crushed stone to allow for powerful reinforcement with strong drainage potential to allow liquid to pass through. They are often used for gardens and planter areas. They are not, however, recommended for supporting structures or slopes.
Hybrid systems combine two or more of these. The important thing to remember about hybrid system retaining walls is that they use both reinforcement and mass for stability. Hybrid walls are also sometimes called composite retaining wall systems.
What Are the Most Common Retaining Wall Materials?
The most common retaining walls include brick, concrete, stone, and wood. Some modern walls use a geosynthetic material called geogrids to stabilize and create reinforced soil.
Concrete Retaining Walls
Concrete is used in a wide variety of applications for retaining walls. They can be made of concrete pillars, poured-on-site solid walls, pre-fabricated walls brought in from elsewhere, or, most commonly in residential areas, concrete blocks.
The advantage of concrete block is that it can be used to create curves and present a variety of architectural styles from Spanish to midcentury architecture. It is only useful, however, for walls under four feet in height because the lack of footings can create issues with wall strength.
Poured concrete walls are stronger than block walls and can rise higher. Like block, poured walls offer various design options, but the skill required to create one properly is specialized. If they are not adequately supported, they can crack, bulge, or wave. They are popular in modern landscaping projects.
Wood Retaining Walls
Wood retaining walls are created using easily-accessible, renewable materials and carry the advantage of having simple construction compared to other types of walls. Wood does not have quite the rigidity and strength of some other materials, so it is only recommended for walls with a maximum four-foot height. It can, however, be used in almost any style of architecture and it easily blends into the natural landscape.
Wood walls can last for twenty years or longer when properly installed and treated with the proper preservatives and waterproofing, but wood does not tend to last as long as other materials. Wood can rot if not maintained, and it may need to be re-treated regularly to maintain its structural integrity.
Stone Retaining Walls
Stone is a time-honored and practical material for building retaining walls. It has many advantages: it is all-natural and eco-friendly and can be used to create any appearance or fit into any architectural style. The solid core of a stone wall can be created to support a structure of almost any height or thickness requirement.
Stone, however, can be tricky and often requires an experienced contractor or landscape architect to design properly. Stone walls can be had in stone veneer or dry / builder stone. Dry stone is a natural solution when dealing with grade changes, but it is difficult to control water flow. Water that builds up inside the wall can destroy its integrity. Thus, it must be designed to allow for drainage. It is popular among country, colonial, and English garden-style landscaping.
Brick Retaining Walls
Brick is another time-honored material used in building, which dates back almost as far as human civilization. It is strong, durable, and long-lasting. However, it creates a solid structure with no room for drainage, so drains must be built into the wall with special care and consideration to preserve the wall’s structural integrity.
Brick is labor intensive and often requires an experienced mason or landscaper to lay correctly. It can, however, result in a durable structure that will last for many decades and can complement any style of landscaping or architecture.
How Are Retaining Walls Different from a Fence?
Fences and retaining walls can be decorative, but their practical intent is completely different. Landscapers and property owners use fences to screen areas. They are not intended to hold back land against landslides, shifting soil, or other practical retention purposes.
The way a fence is built is quite different than a retaining wall since it serves a completely different purpose. One good way to think about it is that a retaining wall is a solid structure designed to hold something back or control the shape of landscaping. A fence is normally designed to cordon off an area to keep someone or something out.
Ready to Redesign Your Yard?
If you are ready to redesign your yard and take its look and form to the next level, Batchelder & Collins is prepared to help. We offer a wide range of landscaping and masonry services, from hardscapes and veneer to vents, doors, and even architectural services. We offer an extensive selection of options including brick, stone, concrete, cement, and blocks. For more information, call us at 757-625-2506 or use our online form today to request an estimate.