Choosing the right geotextile membrane isn't just about selecting the first product you find. One of the biggest factors affecting performance is the membrane's GSM (grams per square metre), but what does that actually mean, and how do you know which weight is right for your project?
Whether you're building a gravel driveway, laying a patio, installing a soakaway or creating a horse arena, selecting the correct membrane can improve stability, drainage and the lifespan of your installation.
In this guide, we'll explain what GSM means, how it affects performance, and how to choose the right geotextile membrane for your product.
What Does GSM Mean?
GSM stands for grams per square metre, which measures the weight of the membrane.
It's important to understand that a higher GSM doesn't automatically mean a "better" membrane. Instead, it indicates the density of the material, which generally influences:
- Durability
- Puncture resistance
- Tensile strength
- Resistance to wear
- Suitability for heavier-duty applications
The right GSM depends entirely on the conditions and intended use.
Does a Higher GSM Mean a Stronger Membrane?
Usually—but not always.
Many people assume the heaviest membrane is always the best choice, but performance depends on several factors, including:
- Whether the membrane is woven or non-woven
- The tensile strength of the material
- The ground conditions
- The expected load
- The drainage requirements
For example, a lighter woven membrane may provide greater stabilisation than a much heavier non-woven membrane because the two products are designed for completely different purposes.
Rather than asking, "What's the strongest membrane?", it's better to ask:
"What geotextile membrane do I actually need for my project?"
Typical Geotextile Membrane Weights
While manufacturers offer a wide range of products, membranes commonly fall into several categories.
Around 100gsm
Lightweight membranes are typically used for:
- Decorative landscaping
- Weed suppression
- Garden paths
- Light domestic projects
They provide separation between soil and aggregates while helping to reduce weed growth.
Around 150–200gsm
Medium-weight membranes are suitable for many domestic landscaping projects, including:
- Patios
- Gravel paths
- Garden landscaping
- General ground separation
They offer a good balance of strength, permeability and ease of installation.
200gsm and Above
Heavier-duty membranes are generally recommended where greater strength is required, such as:
- Gravel driveways
- Parking areas
- Access roads
- Commercial landscaping
- Areas carrying regular vehicle traffic
These membranes are better suited to resisting movement under load and maintaining long-term ground stability.
100gsm vs 200gsm Membrane
One of the most common questions we hear is:
"Should I choose a 100gsm or 200gsm membrane?"
Here's a simple comparison.
| Feature | 100gsm | 200gsm |
|---|---|---|
| Weed suppression | Excellent | Excellent |
| Decorative gravel | ✔ | ✔ |
| Garden landscaping | ✔ | ✔ |
| Vehicle traffic | Limited | Recommended |
| Puncture resistance | Moderate | Higher |
| Longevity under heavy loads | Lower | Higher |
If you're simply laying decorative gravel around flower beds, a lighter membrane is often sufficient.
If you're building a driveway or supporting vehicles, investing in a heavier-duty membrane is usually worthwhile.
Which GSM Do You Need for Different Projects?
Gravel Driveways
For gravel driveways, strength is the priority.
A woven geotextile membrane with an appropriate GSM helps:
- Prevent the sub-base mixing with the soil
- Reduce rutting
- Improve load distribution
- Increase the lifespan of the driveway
This is one of the most demanding domestic applications, so choosing a membrane designed for stabilisation is essential.
Patios
For patios, the ideal GSM depends on the ground beneath.
Stable, free-draining ground may only require a lighter membrane, while softer or disturbed soils benefit from a stronger membrane that helps maintain separation between the soil and sub-base.
Gravel Paths
Garden paths usually experience pedestrian traffic only.
A lighter or medium-weight membrane is often sufficient to:
- Reduce weed growth
- Prevent aggregate migration
- Keep gravel separated from the soil
Soakaways and French Drains
Drainage projects require a completely different type of membrane.
Here, non-woven geotextile membranes are typically used because they allow water to pass freely while filtering out soil particles that could otherwise clog the drainage system.
For these applications, drainage performance is far more important than maximum strength.
Horse Arenas
Horse arenas require a stable, well-separated foundation that can withstand repeated loading.
A woven membrane is commonly used beneath the stone layers to improve stability and help prevent contamination between the sub-base and the underlying ground.
Woven vs Non-Woven Membranes: Why GSM Isn't Everything
Two membranes may both be labelled 200gsm, yet perform very differently.
That's because GSM only measures weight—not how the membrane is manufactured.
Woven Membranes
Designed primarily for:
- Ground stabilisation
- Load distribution
- Separation
- Driveways
- Roads
- Heavy-duty landscaping
Non-Woven Membranes
Designed primarily for:
- Drainage
- Filtration
- Soakaways
- French drains
- Erosion control
Always choose the membrane based on its intended purpose rather than GSM alone.
What About CBR?
Trade customers and civil engineering professionals often refer to CBR (California Bearing Ratio) when selecting a geotextile membrane.
CBR measures the strength of the underlying soil. Lower CBR values indicate weaker ground, which generally requires a stronger stabilisation solution.
While most domestic customers won't need to calculate CBR, it's useful to understand that professional membrane selection is based on both:
- Ground conditions
- Expected loading
- not simply membrane weight.
Is Heavier Always Better?
Not necessarily.
Choosing a membrane that's significantly heavier than your project requires may simply increase costs without providing any practical benefit.
Instead, consider:
- Ground conditions
- Drainage requirements
- Vehicle loading
- Expected lifespan
- Whether you need stabilisation or filtration
Selecting the correct membrane for the application will almost always produce better results than simply choosing the highest GSM available
Frequently Asked Questions
What GSM geotextile membrane do I need for a driveway?
For driveways, a woven geotextile membrane designed for load-bearing applications is generally the best choice. The ideal GSM depends on traffic levels and ground conditions.
Is 100gsm enough under gravel?
For decorative gravel and garden paths, yes. For driveways or areas carrying vehicles, a heavier-duty membrane is usually recommended.
Does a heavier membrane last longer?
In demanding applications, heavier membranes generally offer greater resistance to punctures and long-term wear. However, installation quality and selecting the correct membrane type are equally important.
Can I use a non-woven membrane under a driveway?
Non-woven membranes are primarily designed for drainage and filtration. For driveways and other load-bearing applications, woven membranes are usually the more suitable option.
Choosing the Right Geotextile Membrane
GSM is an important consideration, but it should never be the only one.
The best membrane for your project depends on:
- The type of installation
- Ground conditions
- Expected loading
- Drainage requirements
- Whether you need a woven or non-woven membrane
If you're unsure which membrane is right for your project, our team can help you select the most suitable option—ensuring you get the performance you need without paying for specification you don't.
