There’s no mistake, with thousands of years of history, natural rock retaining walls are among the most reliable. By cutting into a hill or sloped part of your yard and creating level ground both above and below the wall, retaining walls increase the amount of flat, usable ground in a yard. They’re also an attractive way to quickly create borders, manage level changes, or retain soil and areas of ground.
The good news is that building a retaining wall is possible as a DIY project, and if you’re considering an undertaking of your own, here’s a comprehensive guide on how to build a natural rock retaining wall.
The first step for any successful project is careful planning, and a rock retaining wall is no different. Some people like to start with a sketch, but regardless of your method, you’ll need to be able to envision the size and scale of your wall and how it will fit into your current landscape.
This step will include measuring the lengths of the intended wall space and then considering the positioning of elements such as drainage and guttering before starting with any excavation. Think about the color, size, and shape of the stones themself, how high the wall will need to be, and how that relates to your budget.
Before breaking earth, do some searching online about your city’s building codes and regulations. There’s a good chance your local governing body will require an engineer’s stamp on design plans as well as a permit and a potential inspection at the end of the project.
The rules for Fort Collins building and permits can be found on the City of Fort Collins website, where you’ll find whether you need a permit, what is required to submit a permit, how to pay for the required documents, how inspections work, and what to do if your project or plans change.
Currently, Fort Collins regulation requires retaining walls to be designed and stamped by a Colorado Licensed Structural Engineer along with a $100 permit fee. This likely varies from county to county and from state to state, so do your research before beginning.
With your plan in place, you should be able to calculate the amount of rock needed. Again, take into consideration the size of the rocks you would like to build with and determine the number needed per row by dividing the length of the wall by the length of a single block. Keep in mind that the width of the trench should be at least one-half the total wall height.
It’s also usually a good practice to order 10% more stone than you think you’ll need in order to compensate for any waste, compaction, and other errors in your plans for the retaining wall.
You will need to gather all of the required equipment and materials before beginning. The tools and equipment you need include:
The required material includes:
Choosing the right materials for the job is more important than you know. Good quality material will lead to a finished retaining wall that stands the test of time and maintains a great look year after year. Poor quality materials, on the other hand, can lead to a wall that looks cheap and will not endure as well.
This is an especially important consideration when choosing the type of stone for your rock retaining wall. Some people choose perishable materials such as wood to construct their retaining wall. Although it usually looks good for a while, wood degrades quickly with weather and pressure from the elements. This is a similar case with some manufactured stone as it tends to degrade fast in the harsh Colorado climate, eventually developing a chalky-like texture and look.
If you want to make a worthwhile investment in a landscape upgrade, it’s best to choose only the best material that will not only look fantastic but last a very long time as well. We suggest sourcing your stone from The Rock Garden in Fort Collins rather than ordering your stone elsewhere or leaving it up to a contractor to acquire your material. By getting your natural stone from our landscaping store, you’ll benefit from a large selection of different stone materials that you can see in person for yourself. You can also discuss your project with our experts on-site to ensure you are getting the perfect option for your plan.
Once you’re able to get the stone transported to the site where you intend to build the wall, the next step is to organize them by size and shape, sorting them into piles as needed. As a rule of thumb, you’ll want to reserve the largest, flattest stones for the base of the wall and the widest and best-looking stones (which can also be flat, depending on your design) for the capstones at the top of the wall.
The remaining stones can be intermixed throughout the construction process to maintain consistency, and if there are any inconvenient jags and edges that make it difficult to fit a particular stone into the wall, they can be knocked off by your chisel, hammer, or maul.
Now that you have everything organized, you’ll need to mark off the location of the front face of the wall. To do this, hammer in wooden stakes and tie Mason’s line or string around them (use your line level to ensure the string is level).
With the dimensions of your wall planned out, the next step will be to start digging. The base of your wall will require a trench of about a foot (and at least 6 inches deep) and as wide as your base plan needs.
With a full foot in depth, you should have enough room to fill it in with sand, drainage gravel, and the first big blocks that will be the anchor to your base.
Firmly tamper down the base of the trench (to prevent future shifting of the ground level) and cover your excavated trench with landscape fabric, allowing it to run onto the upper-level ground. Strips of fabric should be laid perpendicular to the wall face and should be overlapped with each success strip by about 6 inches. Cut these fabric strips to size with your utility knife.
Before any major stones are put in, you’ll want to apply a layer of drainage gravel. This gravel layer should be 4-6 inches thick to allow proper drainage behind the wall. Rake the gravel flat and even across the trench, then once again use your tamp to ensure it is all level. With the gravel in place, add another one-inch layer of coarse sand over the gravel and tamper it to an even spread.
Lay large, flat stones across the initial base layer of the trench. It’s important to be careful with this first row because it will make a significant difference in the overall level of the rest of the wall. Add or remove sand under each stone and use a level to ensure each remains flat relative to the previous stone. The tops of these bottom layer stones should be flush with one another, and the four-foot level can be laid across multiple to keep everything in check.
Set down the next layer of stone, this time offsetting each stone so that they lay over the top of the first layer’s joints. For taller retaining walls, you’ll also want to set this layer of stone about ½ inch back (toward the slope) from the first layer. This will help your retaining wall resist the pressure of the slope once it is filled in.
Ensure there is as little wobble as possible when the stones are laid down - you can steady them by placing small, flat stones underneath as shims - and make sure the surface of the previous layer is as clean as possible. A clean laying surface is very important, especially if you are using mortar in between each layer as this will ensure good bonding between the stones.
You do not want trapped water behind your wall as it will put unnecessary pressure on the structure. In the backfill area, you’ll need to install a perforated drainage pipe that drains into a soakaway or appropriate area away from the rear of the wall.
When your wall is built to two levels, it’s now time to fill it in behind with drainage gravel. It will be the same technique as when you first excavated the trench base: pour, rake, smooth, tamp, and check level. The gravel should be between the ground behind the wall and the fabric that is up against the wall.
Lay the remaining level of stone using the same techniques as the ones listed for levels one and two. Continue to add ½ offsets to each subsequent level.
An important difference is that, starting with the third level, you want to install “deadman” stones. Deadman stones are long stones that reach back behind the wall into the slope. This helps connect the wall to the ground behind it, providing stability. A deadman should be installed every 4 feet along the wall. Short walls (30 inches or less) require only one level of deadman stones while taller walls should have a second level further up.
Continue adding gravel in the backfill space as you go up.
Be sure to fold the landscape fabric over the backfill gravel in one of the last two layers of stone. Depending on whether you want to grow grass above the backfill portion, leave at least 6 inches at the top and cover it using topsoil.
Lay the final row of stone (capstones), and use masonry adhesive to help keep them in place.
Building a rock retaining wall is an incredibly worthwhile endeavor to improve the aesthetics and functionality of your property. To source the very best stone, whether it’s a DIY project or a contracted job, we encourage you to first plan a visit to The Rock Garden in Fort Collins. We not only have a huge selection of high-quality natural stone, but we can also help you with ideas, tips, and provide expert guidance to ensure your project is a successful one.