Geotextiles, Geogrids & Weed Membranes Explained

Modern patios and driveways rely on more than attractive paving. Much of what determines long-term performance happens out of sight — in the layers of soil, stone and fabric beneath the surface.

One of the most misunderstood parts of that build-up is the use of membranes: heavy-duty geotextiles, geogrids and weed-control fabrics. They are often spoken about as if they all do the same thing. They don’t.

This guide explains what each type actually does, when they genuinely help, and why misusing them often gives a false sense of security instead of durability. It sits alongside our deeper pages on patio structure and failure modes and driveway construction standards.

Two Completely Different Families of Membrane

Before anything else, it’s important to separate membranes into two distinct families:

Structural geotextiles & geogrids – used to manage soil behaviour and load distribution.
Weed-control membranes – used to reduce light reaching the surface and slow weed growth.

Confusing these roles is where many long-term paving and driveway problems begin.

Structural Geotextiles: Separation, Not Magic Reinforcement

Heavy-duty geotextiles are designed to sit between the natural ground and the sub-base. Their job is not to “strengthen” weak soil; it is to manage how the layers interact.

In practice, they are used to:

Separate the sub-base from unstable ground below.
Prevent fine particles (especially clay) migrating into the stone.
Reduce pumping, where wet ground pushes fines into the sub-base over time.
Let the sub-base perform as designed, instead of being slowly undermined.

A useful way to think about them is: they don’t make weak ground strong — they stop good materials being damaged by weak ground.

When Structural Geotextiles Are Genuinely Appropriate

We use structural membranes selectively, most often where soil behaviour would otherwise compromise long-term stability, for example:

Shrink–swell clay soils that move with moisture and tree influence.
Previously disturbed or made ground, such as old patios, trenches and filled areas.
Vehicle loading zones – driveways, parking bays and tracked access routes.
Tree-affected areas, where differential moisture creates uneven bearing.
Transitions between soil types with different movement characteristics.

In these cases the membrane acts as a buffer layer, helping the structure above behave more uniformly.

What Structural Geotextiles Cannot Do

This is where a lot of poor advice creeps in. A structural geotextile cannot:

Compensate for insufficient excavation depth.
Replace proper sub-base thickness.
Correct poor compaction or rushed ground preparation.
Eliminate ground movement altogether.

Soil always moves. Good construction doesn’t try to stop that; it manages it. Membranes support correct build-ups — they don’t rescue incorrect ones.

Geogrids: Load Distribution, Not Decoration

Geogrids are a different tool again. Rather than acting as a filter, a geogrid works through tensile strength, spreading loads sideways across a wider area.

We may incorporate geogrids where:

The ground is particularly soft or vulnerable to deformation.
The surface will see repeated vehicle loading or turning forces.
Old fill or variable subsoils are present beneath driveways or access strips.
Additional stability is needed without further excavation depth.

They are not used routinely, but in the right conditions they can make a meaningful difference to how a driveway or structural patio behaves over time.

Weed-Control Membranes: Light Management, Not Structure

Weed-control fabrics are the thin, felt-like membranes more familiar from garden centres. They are designed to restrict light near the surface, not to carry load or control soil behaviour.

Used correctly, they can work well:

Under gravel paths and decorative stone.
Beneath shingle driveways where the primary structure is elsewhere.
Under bark mulch and planted borders (used with care around long-lived shrubs and trees).

In these settings they slow weed growth and make maintenance easier. What they do not do is reinforce a patio or driveway.

Why Weed Membranes Fail Under Patios and Drives

When placed beneath sub-base and mortar, weed membranes are typically:

Torn by excavation, barrows and compaction machinery.
Too deep to stop seeds that land from above and germinate in joints.
Bypassed entirely by perennial weeds that spread laterally.

This is why you often see weeds appearing through joints despite a membrane being installed somewhere underneath. Most weeds in paving don’t grow up from the subsoil; they colonise from above, exploiting light, moisture and small movements at joints and edges.

The Real Relationship Between Weeds and Paving Quality

In permanent hard landscaping, weed prevention is mainly a function of build quality:

Correct excavation and sub-base depth.
Stable, well-compacted Type 1 or Type 3 sub-base.
Full bedding beneath slabs, with no voids.
Tight, well-finished joints using appropriate products.
Good edge restraint to stop surfaces spreading.

When paving is structurally sound, weed growth tends to be superficial and manageable. When there is movement, joints open and organic matter accumulates — and plants simply take advantage of the opportunity.

Why Blanket “Membrane Use” Is a Red Flag

When membranes are used everywhere, regardless of soil type or loading, it usually reveals one of two things:

A misunderstanding of what the products are actually designed to do.
An attempt to use fabric as a shortcut around proper excavation or materials.

Effective groundworks are context-dependent. What makes sense on free-draining sand may be unnecessary — or insufficient — on shrink–swell clay, and vice versa. This is why site-specific judgement matters.

How Membranes Fit into Patio & Driveway Design

For patios, membranes are considered alongside:

Soil type and seasonal movement.
Drainage strategy and surface falls.
Proximity to trees and root zones.
Finished levels at doors, air bricks and boundaries.

For driveways, additional factors include:

Vehicle weights and turning movements.
Concentrated loads at edges, ramps and pinch points.
Long-term settlement under repeated traffic.

In both cases, membranes are supporting elements. The structure still depends on correct dig, sub-base, laying course and surface specification.

A Quiet Rule of Thumb

If there is one principle worth remembering, it is this:

Membranes should support good groundwork — not be relied on to replace it.

When construction gets the fundamentals right, geotextiles and geogrids work quietly and effectively in the background. When they are used as a sticking plaster, they usually disappoint a season or two later.

Talk to us about patio or driveway groundwork

Related deep-dive guides

Membranes sit between soil and structure. These guides look at the surrounding system — how patios, driveways and drainage are built so that fabrics support good groundwork rather than replace it.

Cross-section diagram showing patio paving layers and sub-base structure

Deeper Knowledge

Patio Construction & Paving Structure

How slabbed areas behave as structural systems: full bedding, bonding, cement curing and why patio failures often start long before anything is visible on the surface.

View paving structure guide →

Diagram showing driveway layers, edge restraint and sub-base depth

Deeper Knowledge

Driveway Construction Standards

How vehicle loading, sub-base depth, edge restraint and drainage come together – and where membranes genuinely help in keeping driveways stable over time.

View driveway standards guide →

Geotextile & Membrane – Frequently Asked Questions

What is the difference between a geotextile and a weed membrane?

Structural geotextiles are heavy-duty fabrics designed to sit between soil and sub-base, helping to separate layers and control fine particle movement. Weed membranes are lighter materials placed near the surface to limit light and slow weed growth. One manages soil behaviour; the other manages surface maintenance.

Will a membrane stop weeds growing through my patio?

Most weeds in paving arrive from above, not from deep in the subsoil. They germinate in joints and at edges where light, moisture and organic matter are present. A buried membrane cannot stop this. Correct excavation, full bedding, tight joints and sensible cleaning are far more important than fabric under the stone.

Do I need geogrid under every driveway?

No. Geogrids are most useful on weaker or variable ground, or where vehicle loading and turning forces are high. On suitable subsoils with correct excavation and sub-base, they are often unnecessary. They are a design tool, not a mandatory extra on every project.

Can membranes replace proper foundations for patios and driveways?

No. Membranes support good groundwork but cannot compensate for inadequate dig depth, thin sub-base or poor compaction. Long-term performance still depends on proper excavation, sub-base, laying course and drainage design, with membranes used where they make structural sense.