Retaining walls are very versatile and uniquely designed structures that hold soil on one side and are free-standing on the other. This type of wall can help you work with uneven topography and changes of grade in a landscape. Proper retaining wall design and construction can help make usable space out of a steep slope, provide a place for landscape plantings and even create a level area for a driveway. On level ground, retaining walls can be used to create an elevated planting area that has improved drainage while creating a place for seating. With proper retaining wall design, you can build a long-lasting and functional structure that will add value to your home or business.
Although a retaining wall may seem like a fairly simple structure that anyone can put together in an afternoon, it is far from simple. Designing and constructing a retaining wall that withstands the test of time requires someone with the knowledge of lateral earth pressure, which is the pressure developed by backfill.
Key Retaining Wall Design Considerations
A variety of important considerations go into the planning of a new retaining wall. You first have to decide the height and length of your wall, and the area where your wall will be placed. Your wall must be the proper height for its location on the slope. It must also have properly compacted backfill, a suitable base and efficient drainage. If you leave out any of these important elements, you may end up with a wall that fails, collects water or is unsafe.
- Suitable Base and Foundation – The base of your retaining wall sets the stage for the finished project. You should start with a suitable base material that is both solid and level. If possible, use soil that has not been used in a landscape environment before this project. This type of soil is sturdier and better suited to supporting a retaining wall. Your excavation contractor should dig the base well below the grade and then add a solid and level foundation. By starting with a level foundation, you can avoid having to use shims that take more valuable time and can reduce the structural integrity of your wall.
- Properly Compacted Backfill – The backfill of your retaining wall is just as important as the wall itself. For this reason, your contractor(s) should take the steps necessary to ensure that the backfill is structurally sound and properly compacted. They should backfill your wall as they go, filling it in at 8, 10 and 12-inch increments against the wall. Then your contractor(s) should thoroughly compact each layer so that you do not end up with sunken areas after the retaining wall is finished.
- Efficient Drainage – Without proper drainage, you could face some serious issues with your retaining wall. Because you are essentially using this structure to hold back several layers of new soil, anything that increases the load that the wall must bear can be detrimental to its structure. When uncontrolled, water can weaken a wall by washing out the base material or collecting behind the wall. Using materials such as gravel under a layer of well-compacted top-soil, drainage channels and drain tiles can help control water flow, channeling it away from your newly-built retaining wall.
- Proper Height – Height is an important aspect of your retaining wall, and not something that should be taken lightly. As a rule, you can build most retaining walls up to a height of 4 feet without having to add additional supports or tiebacks. If you are building anything taller than this, additional elements will be required, and you may possibly need building permits.
Retaining Wall Design – Aesthetic Features
In addition to designing the fundamental structure of your retaining wall, you should also consider many of the additional design features that you may want to incorporate. While a wall creates a natural seating area, do you want to add any specialized seating? Your retaining wall makes a great place for bench seating, built-in lighting and planters that can further enhance the look and function of your landscaping. With the proper planning and a little bit of design savvy, you can create an beautiful new look around your home or business.
If you are planning to build a retaining wall over 4 feet in length, contact New England Enterprises at 508.481.5657 or 508.509.7244 or fill out our contact form. With over 25 years of excavation and landscaping experience, New England Enterprises will make sure that your retaining wall is built right, from the ground up.