Building A Retaining Wall: Everything You Need To Consider

Many residential and commercial properties contain retaining walls for various purposes. Essentially, a retaining wall is a structure built to contain soil that would otherwise slope and potentially erode over time, simultaneously making the land level and useable for other structures, projects or even just a spacious backyard. While these are some of the main functions of a retaining wall; they also serve aesthetic purposes. A well designed and installed retaining wall can add value to your home, especially if it’s well-integrated into the landscaping. Adding a retaining wall is also an easy way to create a garden bed. Lush, green foliage is the best way to bring life to any space. All up, a retaining wall can give your home an easy facelift—without a blow-out budget. In fact, you don’t have to hire any professionals at all. All you need is the right equipment.

If you’re up for a little DIY project this Summer, and are looking for a way to improve your home, then a retaining wall might just be exactly what you’re looking for. To help you along your DIY path, we’re going to show you the easiest way to make a retaining wall for whatever use you may have for it. Read on to discover what goes into building these versatile structures.

When to build a retaining wall

A retaining wall serves many uses. Often retaining walls are built to clear space for a particular feature. They are ideal for those looking to leverage land space. Sloping soil can often be a great waste of space on your land—land that could otherwise serve a useful purpose. You’ll be amazed at how much you can expand your own land space with a retaining wall. Often people build driveways or pools into land that is sloping—this is very much an option for those who have this problem. Plus, not only do these retaining walls serve a functional purpose, but they can be “spruced up” to add visual appeal. Retaining walls are often used as planter boxes. You can design your own eye-catching garden to add a ‘wow-factor’ to your pool, backyard or driveway.

If you’ve decided that you simply must have this feature in your home, there are some things you need to consider—the main thing being equipment. Straight off the bat, you’ll most likely need an excavator and a compactor, but depending on the job, you might also need a mini dumper and specialised attachments like the hydraulic rock breaker, auger with sizeable drill bits, or the concrete sleeper grabber. This all depends on the type of soil you’re excavating and the type of material you plan to build your wall from. Read on for a detailed outline of how you might use this equipment in the construction of your retaining wall.

A retaining wall is the perfect way to bring a little life and colour to the heavy concrete in a pool area.

Check Plans

The first thing you need to know is that you can build a retaining wall up to 1 metre in height in Brisbane without your local Council’s permission. However, if you need to build a retaining wall that is higher, you will have to get building approval from the Brisbane City Council, Moreton Bay Regional Council, or whichever local council depending on where your property resides. You will also need approval if your retaining wall is 1.5 metres or closer to a building, fence line or other retaining wall. If this is not an issue for you, than you do not have to seek approval to build.

If you are building a retaining wall, it must contain ground water drainage behind the wall to relieve water pressure. If you’re building the wall on a boundary, the drainage needs to be on your side of the boundary, along with the wall and the fill. Make sure you accurately establish the boundary line—if you can’t find your boundary pegs, request a copy of your plans from the council or get a surveyor to help. The plans can also tell you if there’s any pipes running underneath your construction which is something you don’t want to disturb. A broken pipe can turn into a very expensive construction. To ensure there isn’t any electrical wires running below ground, get in touch with your energy provider or call up Dial Before You Dig which is an awesome national service which helps reduce the damage to essential infrastructure and harm to individuals when engaging in any excavation projects.

Plan Materials

When you’ve confirmed that there are no pipes or wires interfering with your plans, start marking out where you want to place your retaining wall with spray paint. At this stage, it’s also a good idea to take measurements so you know how much of your wall material you’ll need (for example, how many blocks of concrete or timber sleepers). As a tip, it is a good idea to order 5% extra to cater for any errors or breakage.

The next step is to plan what materials you’re going to use. Often, retaining walls are built with concrete blocks, treated timber, rocks, stones, or bricks. Choosing which material will be best for your retaining wall depends on your budget, the integrity of the material with whatever purpose it will serve (after all, you want this wall to last), and the look you’re trying to achieve. You should aim to make the wall blend in with the rest of your home. The longevity of the wall will depend on the type of material used. Although woods are a cheaper option, in the scheme of things, they may not last as long and will eventually need replacement. Concrete blocks and bricks are a sturdier materials and will increase the lifespan of your wall.

Apart from the material of the wall, you’ll also need to consider what base or footer material to use. The base is an important element as it supports the integrity of the wall—a solid base equals a solid wall. The type of base you need depends on the condition of the soil you’re building on top of and the type of retaining wall (the standard DIY wall is a gravity retaining wall—this wall relies on its own weight to stand). The most common type of base is road base used in combination with sand and cement mix. You can find these things at your local timber and hardware store. Don’t forget to pick up a drainage pipe along with your base materials, and some construction adhesive for the capping stones.

The Foundation

The mini dumper and excavator are a match made in heaven—they take the hard work out of clearing soil and land.

Excavation is required for building retaining walls. For small jobs, a shovel may do the trick—but even then, it’s a pain in the… arms. With all of the digging required, it’s a good idea to source an excavator. For a residential job, you’ll most likely only need a 1 or 2 tonne excavator to get the job done. Ryno Hire offer a one tonne excavator ideal for digging foundations and landscaping work for those hard to reach areas. This machine is the perfect size for doing work around the house; however, if you’re building a retaining wall of a greater height (that has been approved by structural engineers and city council), a 1.7-2 tonne excavator might be more appropriate. The Ryno 1.7-2 tonne excavator is powerful but still very compact, measuring in at only 990 mm in width. Both excavators can navigate tighter spaces and come with attachments, such as augers, to assist with digging post holes, which are necessary when working with most retaining walls.

Quick Tip: Is your soil tough as cement? There could be pieces of hard rock amongst the hardened soil. Don’t strain yourself with extra elbow grease to get these broken up. Use a rock breaker to get the job done. Ryno’s Hydraulic Rock Breaker can be easily attached to 1 to 5 tonne excavators, which you’ll already have for the job. Hire it for the day and you’ll have your groundwork done with ease and time to spare for a tea break.

In regards to the excavation, you’ll need to dig into the wall area as well as the foundation to form a trench around the retaining wall. Dig about 450-500 mm into the wall to give yourself plenty of space to work—remember you’re placing your bricks in the middle of this trench. If you’re building along a slope to stop erosion, you’ll also need to excavate the slope into a step formation. Each step should be in line with a layer of brick and base (so that approximately half of the brick is covered) by the slope—the same goes for the bottom layer. As a rule of thumb, you should always ensure your trench is deep enough for your base and half of your first block for a stable wall.

Quick Tip: Even a residential job requires a lot of transportation of old soil, new soil, base mix, and building materials. It’s a big job trying to move all of this, even with extra hands on site. The cheat code is to use a mini-dumper. The 600kg Mini Hi-Tip dumper is only 700 mm wide, making it compact enough to not get in your way, and sturdy enough to carry just about anything you need. Don’t tire yourself out going back and forth with a wheelbarrow, just let the mini dumper do the job. Save yourself the cardio.

After you’ve excavated the footing for the base, lay 150 mm of road base and use a compactor to get your base flat (down to about 130 mm. Run over the base as least twice with the compactor to achieve this. Ryno Hire’s 49 kg Vibe Plate is the lightest and most maneuverable compactor out of the pack. This compactor is ideal for residential areas and tasks, such as footpaths and small trenches. And it’s affordable to hire too, starting at only A$45 for a one-day job. Top this with a dampened layer (30 mm) of your sand and cement mix. You’ll need to level out this layer for a level wall. After you’ve laid down your sand-cement, you can start laying down your blocks. Get excited because this is when your retaining wall starts to take shape.

Laying Your Bricks

Lay your bricks according to instruction or design—some contain grooves along their sides to guide you. If you base is level then your bricks should lay down nice and flat; however, if you’re working with a wall longer than two metres in one layer of bricks, then you should use a string line to ensure your bricks are in line and level. If you’re using hollow bricks (which I’m sure you are because they’re way lighter!), then you’ll need to fill them with aggregate or scoria to weigh them down. Metal or cement aggregate or scoria is used due to its large pieces—they drain quickly as they let water readily pass through. The last thing you want is water build up weakening the integrity of your wall. After you lay your first layer of brick, place your perforated drain pipe behind it; this is also to stop water build up. Place the end of your drainage pipe at an outlet point—this is usually a spot towards the end of the wall where the water can be released. Then put more of the aggregate or scoria mix on top of the drainage.

Quick Tip: Using solid concrete blocks or concrete sleepers? With these materials, it’s easy to get an injury if you’re not careful or using the appropriate lifting technique. It’ll be worth hiring Ryno’s Concrete Sleeper Grabber to make quick work out of lifting exceptionally heavy material. These can be hooked up to any machine—from excavators to loaders.

Continue laying down your bricks until you’ve reached your top layer. Then, all you need to do is use your construction adhesive to glue down your capping stone. Remember to distribute your adhesive equally so that your capping stones sit level and flat. After this step, it’s just a matter of filling in the backing area with soil and your choice of landscaping. Too easy!

So, is it time for you to get started on your next project? Feel like it’s time you utilise some of the wasted land space around your home? Perhaps a retaining wall is the perfect project for you. Whenever you’re ready to get started, Ryno is ready to supply you with the right equipment and machinery for the job. Gather your list, and we’ll make the arrangements. Get in contact with us today to get the ball rolling.