Retaining Walls: Construction, Function and Aesthetics
We often see retaining walls used as a solution to stop soil erosion along walkways, hills, streams, hiking paths, etc. Over the years these walls have been used in landscaping for much the same purpose. When retaining walls are used in landscaping more than just the function needs to be taken into account, the aesthetics of the wall must be considered in the overall design of the yard. With this idea in place retaining walls have become decorative as well as functional. Below is an overview of the various types of retaining walls, the general construction materials and possible uses within a landscaping design for your home.
There are 4 main types of retaining walls, gravity, cantilevered, sheet piling and anchored. The success of each type depends on the material used as well as the volume of earth being held back.
- Gravity: The gravity wall has a low height of 3-4 feet and relies on its own weight/mass to hold back soil. When constructing the wall the base is thicker than the top and as it narrows the front face leans backwards. This imparts strength visually as well as structurally. Unfortunately retaining walls will need more than visual strength; the gravity wall is easy to topple over impart to the pressure of the earth behind it and there is no additional strength in a gravity wall to account for shifts in the earth.
- Cantilevered: The cantilevered wall is used to hold back much larger amounts of earth than a gravity wall. The wall itself is a uniform thickness, unlike the gravity wall, and is tied to a footing. This footing rests under the earth that the wall is holding in place, this allows the cantilevered wall to use the pressure from the earth to help keep it in place. Because of this, this type of wall is reinforced with steel and generally requires structural engineers to build them. An excellent example of this type of wall is your basement wall.
- Sheet Piling: the piling wall is among the simplest walls to construct and can handle a great deal of pressure if the correct material is used. Generally used in soft soils or in areas where space is limited the pilings are driven approximately 2/3rds below ground with 1/3rd above ground. Height of the wall can be adjusted but as it is increased the wall needs to be anchored into the soil with a tie-back anchor.
- Anchored: Similar to the sheet piling wall in that it has a uniform thickness and is set vertically into the ground however, the anchored wall does not have the same 2/3rd 1/3rd split as the pilings do. This style of wall makes use of anchors which are driven into the rock/earth behind the wall and then expanded mechanically or injected with pressurized concrete. In both instances this creates an anchor within the soil and ties the wall in, this is very useful when the wall needs to have a slender profile and a high load is expected.
Once you have decided on the type of wall you are going to use the question of material comes into play. Typically the 3 main types of material are concrete, rock and wood, each has advantages. Below are a quick overview of the materials and the methods of use.
- Concrete: The most common of materials used currently concrete offers both strength and quick installation. Concrete blocks are stacked and then secured together in several different ways such as interlocking edges, pins and clips. Additionally during installation concrete blocks are laid on top of a packed gravel base allowing the wall to flex with the ground during seasonal changes. One of the main advantages that concrete block has over materials is the height at which a wall can be built. A wall can be anywhere from 30 inches to 30 feet depending on the size of the block used. Generally smaller blocks (12in. x 4in.) are used to accent areas such as gardens, small planter areas and around trees. When walls are built exceeding 30in. then larger bricks are used for strength and stability. These blocks measure upwards of 16-18in. long X 6-8in. high and can weigh anywhere from 50-80lbs. Constructing walls with larger blocks is often a professional job as it requires engineering, excavation and design by licensed engineers. When working with concrete blocks for landscaping it is important to have a design drawn out in order to estimate the number of blocks as well as any specialty blocks needed for the design. The design is also important to help you choose the right block system, weight, design and will help you to troubleshoot problem areas before construction.
- Natural Stone: The rubble wall is iconic; we see them as we drive through the countryside along the roads and separating fields. Built out various sized and colored stones which are tightly fitted together, the rubble wall is both beautiful and time consuming. Additionally the rubble wall is wider at the base and narrows towards the top; this increases the strength of the wall and keeps the earth in place. Building the rubble wall is both a creative and time consuming process, a great deal of time is spent finding the right stones to fit together but the ability to create organic walls that move with the land is truly a bonus to your landscape design.
- Wood Plank or Timber: the third most common material is the plank and timber; this material has been slowly falling out of favor in landscape design and is being replaced with concrete block. Generally the timber/plank is best used with homes that have a rustic appearance. This type of wall can be made with planks (your regular 2×4, 2×6, 2×8 etc.) or more commonly with timber (4×4, 4×6, 6x6s). This method allows you to quickly build strong walls with steps, multiple angles and rarely exceeds more than 4foot high.
We now know the types of walls and the materials but what about how they are used? Today’s’ landscaping is much more than just lawncare schedules and fertilizing! Retaining walls allow the homeowner to have a variety of features added into their property. Several possibilities are:
- Water features: Ranging from elaborate Koi ponds and cascading waterfalls to small ponds with a single waterfall, the retaining wall aids in the construction of water features and allows for more complicated designs to be realized.
- Terraced gardens: if your property has a steep slope and really prohibits you from realizing your landscaping plans, retaining walls can be used to create terraces. These walls combined with deep rooting plants work together to keep the earth in place and help you to reclaim lost space.
- Gardens: If you are a gardener, you want to keep your landscape design and still be able to garden; the timber retaining wall may be the best choice. With a simple timber retaining wall you can create raised bed gardens that will match the rest of your landscaping.
The most important part of landscaping is making sure you have a competent and professional landscaping company working with you. At All States Landscaping, one of the premier Utah landscaping companies, comprehensive services such as elegant retaining walls, decorative concrete, residential and commercial sprinkler systems are available. All States Landscaping has 26 years of experience working with the Utah community to transform the everyday yard to stylishly landscaped experiences. For more information on how All States can meet your landscaping needs: Please Contact Us!