Non Woven Geotextile Membrane - Is Thicker Always Better?

A thicker non woven geotextile membrane is stronger, but strength alone does not define performance. As weight increases, permeability and flexibility change. For many projects, especially those involving drainage, using an overly thick membrane can reduce effectiveness rather than improve it.

There is a correct grade for each job. The aim is to balance strength, filtration and water flow without overspending or compromising drainage.

What Non Woven Membranes Do

Non woven geotextile membranes are used for separation, filtration, protection and weed control. Installed between soil and aggregate layers, they stop fines migrating upward while allowing water to pass through. This keeps sub bases stable and drainage systems working as intended.

All non woven membranes do this job, but they perform differently depending on how they are made and how heavy they are.

Understanding Thickness and Manufacture

Two manufacturing methods are used:

• Thermally bonded
  Fibres are fused at contact points. This creates a flatter, stiffer membrane with high permeability at lower weights.

• Needle punched
  Fibres are mechanically entangled to form a thicker, three dimensional structure. This improves cushioning and strength but can reduce water flow as weight increases.

As membranes get heavier, permeability generally decreases. That is why thicker is not always the right choice.

Choosing the Right Grade

NW6 / EG80 - 80gsm This is the lightest non woven membrane in the range. Thermally bonded, stiff and highly permeable. Best suited to gardens, landscaping, grid systems and applications where drainage matters more than load bearing. Ideal when strength demands are low but filtration needs to be reliable.
NW8 - 100gsm The most widely used non woven membrane. Still thermally bonded, but with improved strength over EG80. Suitable for driveways, patios, soakaway crates and general separation. A strong all round option for domestic projects and light trafficking.
NW18 - 215gsm A step up in durability. This membrane is both thermally bonded and needle punched, giving increased puncture resistance while maintaining good drainage. Used where traffic is heavier, including driveways with regular vehicle use and busy access areas.
SNW40 - 300gsm A needle punched membrane offering cushioning and reinforcement. Permeability is lower than lighter grades, but strength is higher. Commonly used in commercial horse arenas, rail projects and areas where impact protection and load distribution matter.
SNW80 - 650gsm The heaviest non woven membrane stocked. Designed for very demanding conditions such as landfills, coastal erosion control and sea defence. It reinforces weak ground and protects liners, but is not suitable where fast drainage is required.

Key Takeaway

Thicker membranes are not better by default. For drainage led projects, a lighter thermally bonded membrane often performs best. Heavier needle punched membranes are used where reinforcement, protection or load distribution is the priority.

Choosing the correct grade avoids drainage issues, unnecessary cost and installation problems later on. If you are unsure which weight suits your ground conditions, traffic level or drainage requirements, share the details and we will advise the correct membrane.