Geofabric behind a retaining wall prevents the drainage failure that causes most wall collapses.
Water pressure is the silent killer of retaining walls. When rain soaks into soil behind a wall, hydrostatic pressure builds and pushes against the structure from the inside. Without a drainage layer protected by geofabric, that pressure has nowhere to go.
This article covers which geofabric to choose for a retaining wall, how to install it step by step, and the mistakes that cause premature wall failure. Whether you are building new or fixing drainage on an existing wall, the right geotextile is the difference between a wall that lasts five years and one that lasts fifty.
New to geofabric? Start with our guide on what geofabric is and how it works. Browse the full erosion control range for every product mentioned in this article.
Geofabric, also called geotextile fabric, sits between the drainage aggregate behind your retaining wall and the native soil. It performs two jobs simultaneously. Water passes through the fabric freely while fine soil particles are blocked from migrating into the drainage layer. Without this barrier, soil particles gradually infiltrate your drainage aggregate through a process called soil migration. Over three to five years, your crushed rock turns into a dense, waterlogged mass that cannot drain. Once the drainage layer is compromised, hydrostatic pressure builds against the wall and pushes it outward. The geofabric also maintains physical separation between material layers. Your drainage aggregate stays clean. Your native clay or loam stays where it belongs. This separation is what keeps drainage working decades after installation.
Geofabric prevents:
Every one of these failures traces back to water with nowhere to go. The Australian Department of the Environment recommends geotextile separation in erosion and drainage control applications for exactly this reason.
For retaining wall drainage, you specifically need non-woven geotextile fabric. Non-woven geotextile has randomly arranged fibres needle-punched together, creating thousands of tiny drainage pathways throughout the material. Woven geotextile, by contrast, is designed for soil reinforcement and load distribution under roads and pavements.
The distinction matters more than most people realise. Woven fabric has a tighter weave that restricts water flow, which is the opposite of what you want behind a retaining wall. Using woven geotextile behind a wall actually traps water rather than draining it. If you are buying geofabric for a retaining wall project and the product label says "woven", put it back.
| Feature | Non-Woven (Use This) | Woven (Do Not Use) |
|---|---|---|
| Water flow | High. Drains freely through fibres | Low. Tight weave restricts flow |
| Filtration | Blocks fine particles while passing water | Particles clog the weave or pass through |
| Primary use | Drainage, filtration, separation | Soil reinforcement, load distribution |
| Typical weight | 100 to 200gsm | 70 to 150gsm |
| Behind retaining walls? | Yes | No |
For most residential and commercial retaining walls in Australia, a 100gsm non-woven geotextile is the standard specification. All Stake Supply stocks filter fabric geotextile non-woven drainage membrane in widths from 0.60m to 4m. For walls under 1.2m, the 1m wide roll handles the job. Taller walls or deeper drainage zones suit the 2m wide option.
Installing a geofabric retaining wall drainage system follows a specific sequence that most DIY guides get partly wrong. The fabric does not simply hang against the soil. It wraps around the drainage aggregate to form an enclosed drainage envelope that keeps aggregate clean for decades. Get the wrapping wrong and you end up with the same clogged drainage you were trying to prevent.
These steps apply to timber, concrete block, and stone retaining walls:
Pin every fold and overlap. Unpinned geofabric shifts during backfilling and creates gaps where soil migrates straight into your drainage layer. Steel fastening pins (170 x 75mm) are purpose-built for securing geotextile in drainage applications.
Step 6 is the one most builders rush past. Folding the fabric over the top creates a complete envelope around the drainage aggregate. Skip this fold and topsoil washes down into the crushed rock from above, clogging your drainage within a couple of wet seasons.
Most retaining wall drainage failures come down to installation errors, not product faults. The geofabric itself is straightforward to work with. Getting it in the right place at the right time during the build sequence is where projects fall apart.
Every one of these mistakes produces the same outcome: a drainage system that works for a year or two, then quietly fails. The wall starts leaning, cracking, or bulging, and the repair costs far more than the original drainage would have.
The honest answer is almost never. Any retaining wall taller than 400mm that holds back soil needs drainage behind it, and drainage needs geofabric to stay functional long term. The only genuine exception is a freestanding garden wall that does not actually retain soil on either side.
If both sides of the wall sit at the same ground level, there is no soil pressure and no drainage requirement. Decorative garden edging under 400mm on free-draining sandy soil is another borderline case where some builders skip the drainage layer. For everything else, the fabric goes in.
You must use geofabric when:
When in doubt, include it. A 1m x 50m roll of non-woven geotextile from All Stake Supply costs under $90 ex GST. Rebuilding a failed retaining wall costs thousands.
Calculate the total length of your wall, then add 10% for overlaps at joins. For width, measure the depth of your drainage zone and add enough for the base fold and top fold. A 1m high wall with a standard 300mm wide drainage zone typically needs fabric about 1.5 to 2m wide.
| Wall Height | Drainage Width | Geofabric Width Needed | Recommended Product |
|---|---|---|---|
| Under 600mm | 300mm | 1m | 1m x 50m roll |
| 600mm to 1.2m | 300 to 400mm | 1.5 to 2m | 2m x 50m roll |
| 1.2m to 2m | 400 to 500mm | 2m+ | 2m x 50m roll |
| Over 2m (engineered) | Per engineer spec | 4m | 4m x 100m roll |
For residential projects, the 2m x 50m roll handles most jobs with material to spare. Commercial and civil projects typically use the 4m x 100m roll for efficiency on longer runs.
You also need steel fastening pins to secure the fabric at all folds and overlaps. Budget one pin every 300mm along every fold line and overlap seam. For a 10m retaining wall, that works out to roughly 50 to 70 pins. The CSIRO notes that soil movement behind retaining structures is most active in the first two wet seasons after construction, so proper pinning during installation is worth the effort.
A geofabric retaining wall drainage system is simple to install and costs a fraction of the wall itself. Non-woven geotextile keeps your drainage layer clean for decades, provided you wrap it properly and pin every fold.
Browse the full range at All Stake Supply or contact the team for trade pricing and bulk orders on geotextile and fastening products. All orders ship complete from the St Marys warehouse, delivered anywhere in Australia.
