What Geotextile Fabric Should You Lay Under a Gravel Driveway?

For most New Zealand gravel driveways, a non-woven polypropylene geotextile fabric rated at 150–200 gsm (grams per square metre) is the right choice. It separates your subgrade soil from the gravel above, stops stones from sinking into soft ground, suppresses weeds, and allows water to drain through — all without rotting or degrading for decades when installed correctly.

Why Geotextile Fabric Matters Under Gravel

Without a separation layer, gravel gradually migrates downward into soft or clay-heavy soil — a common issue across many NZ regions where soils can be wet and poorly drained for much of the year. Over time, your driveway develops ruts, soft spots, and an uneven surface that's expensive to fix. A good geotextile fabric:

• Separates the subgrade from the aggregate layer
• Stabilises the surface under vehicle loads
• Filters water through while holding fine soil particles back
• Reduces the depth of gravel needed (saving material costs)
• Suppresses weed growth from below

Choosing the Right Fabric Type

There are two main types of geotextile fabric available at NZ suppliers:

For a standard residential gravel driveway, a non-woven fabric at 150–200 gsm is the most widely recommended option. It has excellent filtration properties and handles the separation job well.

If your driveway will take heavy vehicle traffic — such as trucks, trailers, or farm machinery — consider stepping up to a woven geotextile at 200 gsm or higher, or seek advice from a geotechnical professional, as subgrade conditions and load requirements vary significantly.

What About Weed Matting?

Standard garden weed matting is not a suitable substitute. It is not engineered for load-bearing separation, breaks down faster, and can impede drainage. Always use a product specifically rated as a geotextile separation fabric.

How to Lay Geotextile Fabric Correctly

Proper installation is just as important as choosing the right product. Follow these steps:

1. Excavate and prepare the subgrade. Remove topsoil and organic material. The depth will depend on your soil type and expected traffic — as a rough guide, 150–300 mm of compacted aggregate is common for residential driveways, but get local advice if your soil is soft or expansive clay.
2. Grade and compact the subgrade. A plate compactor or roller will help. Address any soft spots with additional fill before laying fabric.
3. Roll out the geotextile. Lay it across the full width of the driveway, running up the sides of any edging or batter slopes. Avoid stretching it tight — leave a little slack.
4. Overlap joins by at least 300–500 mm. Where two rolls meet, overlap generously and, on sloped driveways, ensure the uphill sheet overlaps on top of the downhill sheet so water doesn't lift the edge.
5. Pin or peg the fabric temporarily if it's windy, using U-shaped ground staples.
6. Place aggregate immediately. Don't leave fabric exposed to UV for extended periods, as sunlight degrades polypropylene over time. Cover with your chosen gravel or crushed rock promptly.
7. Compact the aggregate in layers. Typically 100 mm compacted lifts, working up to your finished depth.

Choosing Your Gravel

The fabric works best under angular crushed aggregate (such as AP40 or AP65 basecourse) rather than round river stones, which don't interlock and can shift under load. Check with your local quarry or supplier for what's available in your region — aggregate types and naming conventions vary around NZ.

NZ Climate and Soil Considerations

NZ's varied climate means soil conditions differ widely. In areas with high rainfall (much of the West Coast, Northland, and parts of the Waikato), subgrade soils can become saturated and lose bearing capacity quickly — making a quality geotextile even more important. In drier regions, a lighter fabric may suffice, but separation is still worthwhile. If you're on expansive clay soils or a site with poor natural drainage, it's worth getting a professional assessment before you start.

BRANZ publishes useful guidance on ground conditions and moisture management relevant to NZ construction.

Do You Need a Building Consent?

In most cases, a standard residential driveway does not require a building consent under Schedule 1 of the Building Act — but this depends on your specific site, local council rules, and whether any earthworks are involved. Always check with your local council before starting, especially if significant earthworks, retaining, or stormwater changes are involved. MBIE Building Performance has helpful guidance on when consent is required.

When to Call a Professional

While laying a geotextile fabric and gravel driveway is within reach of a capable DIYer, there are situations where you should bring in a qualified driveway layer or civil contractor:

• Your subgrade is soft, waterlogged, or made up of fill material of unknown quality
• The driveway is on a significant slope (erosion and drainage design become critical)
• You need heavy vehicle access (engineering input may be required)
• The project involves significant earthworks, retaining walls, or changes to stormwater flow
• You simply want the job done right the first time with the correct compaction equipment

You can find experienced local driveway layers and civil contractors on tradedirectory.co.nz.

Sources & Further Reading

• BRANZ – Building Research Association of NZ
• MBIE Building Performance – Consents & Exemptions
• Bunnings NZ – Geotextile & Landscaping Fabrics
• Mitre 10 NZ – Driveway & Landscaping Products
• PlaceMakers NZ – Civil & Drainage Products
• WorkSafe NZ – Safe Work on Site