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Building a Retaining Wall? 5 Quick Tips to Get You Started

Apr 6, 2017

Building a Retaining Wall? 5 Quick Tips to Get You Started

Using retaining walls for your landscaping is an excellent way to add definition and improve the functionality of your lawn, garden or outdoor space. A retaining wall is simply a structure that holds soil behind it. Depending on exactly where you are installing your retaining wall, there are several ways to construct them. This quick guide lays out five hints and tips to get you started!

1. What type of wall do you need?

You will need to consider what exactly is above your wall: is it something relatively lightweight, or something heavier like a swimming pool? If you are using a shorter wall, you can install what is known as a gravity wall, which supports itself with its own weight. These are generally constructed from stone, mortar, lumber, or boulders. Your other option, if the retaining wall is taller, or needs to bear a greater load, is to install a reinforced wall. As its name suggests, a reinforced wall is held in place with something else, such as concrete, rebar, or other materials that strengthen it.

One of the best choices for constructing a retaining wall of either type is wood. A wooden retaining wall will have a beautiful, natural look to it that will fit with a variety of different aesthetic styles. Using lumber and timbers that you source at a lumberyard is a great choice because they are easy to construct and the materials are relatively inexpensive. There are some considerations to be aware of when using wood as a retaining wall to ensure your wall will hold up and last for many years.

2. Has the wood been treated?

The vast majority of wood retaining walls are constructed using lumber that has been pressure treated to prevent rot and there are different levels of treatment to consider. Untreated lumber can very easily begin to decompose, dramatically reducing the life of your retaining wall. Because the wood you use in the construction of your retaining wall will be constantly exposed to the elements in a way that other wooden structures will not, you should ensure that any lumber you purchase is treated for ground contact. Look on the label for Heavy Duty Ground Contact treated wood; this will ensure that your retaining wall has been prepared to deal with the elements for years to come. Lumber that has been heavily treated is injected with preservative, which will leave small indentations in the wood.  There are also boards that have been ‘surface treated’, which do not have the same pock marks, so they are smoother and more attractive, but they will generally not last as long in a ground contact setting.

3. What should I look for when buying lumber?

There are several common species of wood that are commonly used for pressure treated lumber, including Douglas Fir, Hem Fir, Ponderosa Pine and Southern Yellow Pine. The exact species you find at your local lumberyard will depend upon which region of the country you are in, but all should be considered good options as long as they are treated for ground contact. 

The next biggest consideration is going to be the size of the vertical posts and horizontal retaining members. For posts, you will most likely be using 4x4, 4x6, 4x8 or 4x10s.  The required size will depend on how much load you will be placing on the posts.  Naturally, the larger the post, the stronger it will be. The load will depend on a combination of the height of the wall, along with how far you are spanning between posts.  For the actual retaining members, most people use 2x4 or 2x6 boards, but again your exact choice will depend on the load, which heavily depends on how far you are spanning, and also the aesthetic look you are wanting to achieve.  For increased strength and span, consider using crisscrossing supports, or straps attached behind your wall.  For more specifics on what size lumber you will need for your exact plans, speak with the experts at your local lumberyard, or a contractor with experience in building retaining walls. They can help you pick out the right materials and give you valuable tips and tricks to help you during your construction.

4. Constructing your retaining wall

Once you’ve picked out the materials you will be using, you’ll need to begin considering your specific needs regarding the construction of your retaining wall. You will want to mark out the area where you will be doing construction using a guide string. Once you have done this, you can begin digging a trench in the dirt and measuring out the lumber you will need.

To build your wall, you will start with a foundation, which you will pin into place using rebar. You will want to carefully drill holes for the rebar in your foundation beams to hold the whole structure together. Once you begin laying the lumber in the trench you have dug, it’s essential that the wood remain level. Use a level to periodically check that the lumber has not shifted or become crooked inside the trench. Next, build your wall up to your desired height and add a top cap to complete the work you’ve done.

5. Where do I get the lumber?

In order to ensure you have the best quality materials, you’ll want to head to a place that specializes in lumber. A simple hardware store will not be enough, you will want a true lumberyard. In the Chicagoland area, Hines Supply is a great place to get high-quality lumber, as well as advice from experts on what you need specifically for your construction project.

You may also wish to seek the services of professionals to aid in the construction of your retaining wall, particularly when building a reinforced wall. While this is a project you can potentially do yourself, it may be easier to secure the services of a contractor. Once again, a company like Hines Supply can help provide you with an estimate for the cost of the project, expert advice and suggest a contractor, if you need.