A DIY retaining wall project could add the striking flair to lift your landscaping. Not only do retaining walls increase functionality and the usable space in your front or back yard, but they also create a premium look and ultimately boost the value of your property.
Unlock endless options for your outdoor space: a retaining wall can make tiered gardens, terraces and sunken fireplaces possible. Keep reading to find out exactly what you need to consider when planning your very own DIY retaining wall project.
Case Study: Kate Sparks transforms entire outdoor area using DIY retaining walls
Do I need Council approval?
Different zones have different requirements. It’s best to check with your local council prior to construction to ascertain if approval or building permits are required.
Find your local government in these handy directories:
NSW – QLD – VIC – NT – SA – WA – TAS – ACT
Do I have a cut site or a fill site?
A cut site is when you are cutting into the natural slope of the land to create a stepped site with your wall. A fill site is when the wall is installed at the lowest part of a gradual slope and then filled to level it with the highest part. Different sites will require slightly different procedures and equipment.
What kind of soil am I working with?
To test the soil at your site, take a handful from at least 300mm below the surface and squeeze.
- Organic soils will stick together but won’t hold – these should only be used as top soil and not to build the wall itself.
- Clay soils will form a ball – they retain moisture and add pressure behind walls, so they may require additional reinforcement but can still be used in your project.
- Sandy soils won’t stick at all – they are granular and allow for good drainage, making them ideal for retaining walls.
Do I need to compact my soil?
Soil should only be compacted away from the zone of influence and should not be compacted against the retaining wall itself, or in any way that could affect the back fill or drainage capabilities. Fill sites would generally require some compacting to stabilise the fill, but cut sites generally will not, as you are excavating through already stable soil.
Do I need any specific equipment/machinery?
The equipment or machinery required will depend on the type and purpose of your DIY retaining wall project and unique site conditions.
For instance, a fill site will probably need compacting to stabilise the soil, so a plate compactor/vibrating plate may be needed, whereas a cut site may require an excavator if it is of a significant size. Always consider the best way to move materials to avoid injury or unsafe labour practices (particularly in difficult-to-reach or tight areas).
How do I measure my site?
A detailed site plan, drawn to scale, will be helpful when estimating and calculating the materials you’ll need. Measure the length and height of the proposed wall and determine how much weight it will need to retain to choose the most appropriate retaining solution. A clear site plan will also help to calculate exact measurements of the required materials.
Once you’re ready to install your retaining wall, clear the area and prepare your site. Use stakes and spirit-levelled string lines as a guide to install in accordance with your site plan.
Why is waterproofing important?
Timber is typically more susceptible to water damage than cement. However, whichever material you choose should still be waterproofed before backfilling, to increase material longevity. Use a commercial waterproofing or bituminous product such as SikaTite BE, to ‘paint’ the underground portion of the material. Then, use a commercial–grade polyurethane sealant, such as Sikaflex Pro, to seal any gaps or crevices.
How do I correctly backfill my wall?
Drainage is crucial, as trapped moisture can cause irreversible damage and a premature weakening of the wall.
Before backfilling, lay an agricultural line or pipe at the base of your wall to allow the release of underground seepage. Ensure you also line it with an external filter sock to prevent silt from entering and clogging it. This pipe should exit at the sides where it can run off; avoid cutting into your wall to fit the pipe though, as it can undermine the strength of the wall.
You should also use backfill that’s granulated to allow for adequate drainage; denser soils that hold moisture will add dangerous pressure to the wall.
Is angling or stepping back my wall important?
Whether you install your wall straight or at a slight angle/step depends on its height. This factor is particularly important when working with larger or taller retaining walls.
Gravity will work against a wall that is exactly perpendicular to ground level. This will direct most pressure to the lower part of the wall.
To avoid any significant pressure to the base of your retaining wall, keep a very slight angle when installing: the bottom of the wall should protrude slightly more than the top. However, if the wall is only a minimal height, for example, in a small garden bed, don’t worry too much.
Add flair and boost functionality with a DIY retaining wall project
By following this comprehensive guide, you’ll be well-prepared to tackle your DIY retaining wall project with confidence. Whether it’s ensuring proper drainage or understanding the importance of backfilling and waterproofing, each step is crucial for a successful build. Level up your yard and unlock the potential of your outdoor space today!
