Geotextile drainage fabric is the layer between your aggregate and the surrounding soil that stops sediment from destroying drainage systems.

Every French drain, retaining wall drain and subsoil pipe system relies on clean aggregate to move water. Without a geotextile filter layer, fine soil particles migrate into the gravel bed and block flow. Most failed drainage jobs trace back to missing or wrong fabric.

This guide covers how to pick the right type and weight of geotextile drainage fabric, where to use it, how to install it properly, and the mistakes that cause premature failure.

What Is Geotextile Drainage Fabric?

Geotextile drainage fabric is a permeable synthetic textile made from polypropylene or polyester fibres. The fibres are needle-punched together (not woven), which creates thousands of tiny pores that let water pass through while trapping soil particles. It acts as a filter between your drainage aggregate and the surrounding earth.

Without this separation layer, soil migrates into the gravel over time. The aggregate fills with sediment, water flow drops, and within 12 to 18 months a perfectly good drainage trench becomes a clay-packed channel that does nothing.

• Filtration keeps fine particles out of aggregate beds
• Separation stops gravel mixing into subsoil under load
• Drainage allows water to pass freely in all directions
• Durability resists UV, biological degradation and most chemicals
• Lifespan of 50+ years when covered with aggregate or soil

All Stake Supply stocks non-woven drainage membrane rolls in widths from 0.6 m to 4 m, all at 100 gsm, which suits the majority of residential and light commercial drainage work.

Woven vs Non-Woven Geotextile for Drainage

This is where most mistakes start. Woven and non-woven geotextiles look similar on the roll but behave completely differently in a drainage application.

Non-woven fabric is the only correct choice for drainage. Woven geotextile has high tensile strength but very low permeability, which means it blocks water instead of filtering it.

If your supplier offers both, ask specifically for non-woven geotextile filter fabric. All Stake Supply's 4 m x 100 m drainage membrane roll is the go-to for larger commercial and civil drainage projects.

How to Pick the Right GSM Weight

In Australia, geotextile weight is measured in grams per square metre (gsm). Heavier fabric filters finer particles but passes water more slowly. The trick is matching gsm to your soil type.

Sandy soils drain easily and only need light filtration. Heavy clay soils carry very fine particles that demand a denser fabric.

• For most backyard French drains, 100 gsm non-woven fabric handles the job
• If you are working in heavy Sydney basin clay, step up to 150 gsm for better particle retention
• Check the manufacturer's flow rate specs if the project has engineering requirements (the Standards Australia AS 3706 series covers geotextile testing methods)
• Thicker is not always better. Oversized gsm restricts water flow unnecessarily

All Stake Supply's 2 m x 50 m rolls at 100 gsm cover the sweet spot for residential and garden drainage work. For tighter access areas, the 0.6 m wide rolls fit standard 300 mm trench work without excess trimming.

Where to Use Geotextile Drainage Fabric

Geotextile drainage fabric belongs anywhere you are placing aggregate around pipe or using gravel as a drainage medium. Skipping it saves ten minutes on install and costs you thousands in remediation when the system silts up. Here are the most common applications.

French Drains

Line the entire trench with non-woven geotextile before adding gravel and slotted ag pipe. Leave enough fabric on each side to fold over the top of the aggregate once the pipe is in place. Pair it with 100 mm socked ag pipe for double filtration.

Behind Retaining Walls

Place geotextile between the retained soil and the gravel drainage zone behind the wall. This stops soil washing through the weep holes and staining the wall face. Run the fabric from the footing to the top of the backfill.

Under Paved Areas and Driveways

A geotextile layer between the subgrade and the road base prevents the base course from punching into soft soil. It also allows groundwater to drain away instead of pooling under the pavement and causing heave. The Australian Department of the Environment references geotextile separation layers in several erosion and sediment control guidelines for construction sites.

• Around soakaway pits to prevent sediment filling the pit
• Under permeable paving systems
• Wrapping rubble drains on slopes and embankments
• In agricultural drainage across paddocks and orchards

How to Install Geotextile Drainage Fabric Step by Step

Proper installation is the difference between a drainage system that lasts decades and one that fails within two years. The steps below apply to a standard French drain or subsoil drainage trench.

1. Dig the trench to the required depth and grade. Remove any sharp rocks, roots or debris from the base and walls.
2. Grade the base at a minimum 1% fall (10 mm per metre) towards the outlet.
3. Line the trench with geotextile. Cut the fabric wide enough so it covers the base and both walls with 300 to 450 mm of overlap at the top.
4. Lay a 75 mm bed of clean gravel on top of the fabric at the base of the trench.
5. Place the ag pipe on the gravel bed with the perforations facing down.
6. Backfill with gravel around and over the pipe until the trench is full to within 150 mm of ground level.
7. Fold the fabric over the top of the gravel, overlapping the two sides by at least 300 mm.
8. Backfill the final 150 mm with topsoil or turf to finish.

Use steel fastening pins to hold the geotextile in place along the trench walls during backfilling. Pin every 200 to 300 mm on slopes to stop the fabric slipping before the gravel goes in.

Mistakes That Wreck Drainage Systems

Drainage remediation is expensive. Digging up a failed French drain, removing contaminated gravel and re-laying the system costs far more than the original install. Research from CSIRO on soil-fabric interaction confirms that incorrect geotextile selection is one of the leading causes of subsurface drainage failure in Australian conditions.

• Using woven geotextile or weed mat instead of non-woven filter fabric. Both restrict water flow and defeat the purpose of the drainage system.
• Insufficient overlap at joins. Water carrying soil particles bypasses the fabric through gaps. Minimum 300 mm overlap, shingled in the direction of water flow.
• Skipping fabric entirely because the gravel 'looks clean enough'. Soil migration is invisible until the system is already clogged.
• Laying fabric on rough subgrade with sharp rocks or cut roots. Punctures create entry points for sediment.
• Not wrapping the full pipe envelope. The fabric must surround the entire gravel and pipe assembly. If it only sits underneath, sediment enters from the top and sides.

Ordering Drainage Fabric in Bulk

Landscapers, civil contractors and councils running multiple drainage jobs need reliable supply without waiting on backorders. All Stake Supply has been a family-owned Australian business since 1976, with 1,000+ products in stock at the St Marys NSW warehouse. Every order ships complete, so you are not left on site waiting for a partial delivery to catch up.

• Rolls available from 0.6 m to 4 m wide
• Lengths from 50 m to 100 m per roll
• 100 gsm non-woven as standard, suitable for most drainage applications
• Geotextile filter tubes also available for wrapping individual pipe runs
• Delivers Australia-wide

Browse the full product range or contact the team for trade pricing and bulk orders.

Get the Right Fabric Before You Start Digging

Picking the correct geotextile drainage fabric takes five minutes. Fixing a silted-up drainage trench takes days. Go with non-woven, match the gsm to your soil type, overlap your joins by at least 300 mm, and wrap the entire aggregate envelope.

All Stake Supply stocks non-woven drainage membrane rolls in every width you will need, along with ag pipe, fastening pins and filter tubes. One order, complete delivery, no waiting around on site.