4.5m x 100m Geotextile Filter Membrane / Drainage Fabric 80g (450m2/Roll)

What is 4.5m x 100m Geotextile Membrane? 

4.5m x 100m Geotextile Membrane is a 80gsm (grams per square metre) nonwoven Filter Membrane, supplied as a 4.5m x 100m roll covering 450m2. 

Its 80gsm weight places it as a light-duty fabric, suiting it to filtration and separation tasks where high mechanical strength or significant load-bearing stabilisation is not the primary requirement.

Its principal functions are:

• Filtration: This is a key purpose. The fabric acts as a filter, permitting water to move into drainage systems (like French drains or around perforated pipes) while preventing fine soil particles, silt, and sand from entering and causing blockages. 
• Separation: It serves as a dividing layer between different soil types or between soil and aggregate layers (e.g., in soakaways, or between topsoil and a drainage layer in planters). This prevents the intermixing of materials, which could compromise drainage performance.
• Drainage (Facilitation): While the fabric itself doesn't "drain" in the sense of carrying water away over long distances (like a pipe), its high permeability allows it to act as a conduit, facilitating the passage of water into a designed drainage system or layer.

Benefits

• Optimised Filtration Performance: Specifically designed with pore sizes that effectively retain soil particles while allowing high rates of water flow, preventing clogging of drainage systems.
• Enhanced Drainage System Longevity: Protects drainage aggregates and pipes from siltation, ensuring they function efficiently for longer.
• Effective Soil Separation: Prevents the intermingling of different soil or aggregate layers, maintaining their distinct properties and functions.
• Lightweight & Flexible: The 80gsm fabric is easy to handle, cut, and conform to various trench shapes or ground contours, simplifying installation.
• Large Roll Coverage (450m²): The 4.5m x 100m roll provides extensive coverage, ideal for larger drainage schemes or landscaping projects, reducing the number of joints.
• Durable & Rot-Proof Material: Manufactured from synthetic fibres that are resistant to rot, mildew, and common soil-borne chemicals.
• Cost-Effective Solution: An economical way to improve the performance and lifespan of drainage systems and maintain the integrity of separated soil/aggregate layers.

Applications

• French Drains & Land Drains: Lining trenches and wrapping perforated drainage pipes to prevent soil ingress and maintain clear water flow.
• Soakaway Crates & Systems: Wrapping soakaway units or lining soakaway pits to ensure long-term filtration and prevent clogging by surrounding soil.
• Aggregate Driveways (Separation/Filtration Only): As a separator between the sub-grade (soil) and the sub-base (hardcore/MOT Type 1) in very light-duty domestic driveways with excellent ground preparation and a robust sub-base, where its primary role is to prevent fines migration and help maintain sub-base integrity through good drainage. It is not intended for significant ground stabilisation in driveway applications.
• Paths & Patios: As a separation and filtration layer beneath permeable paving or lighter-use pathways.
• Retaining Wall Drainage: Placed behind retaining walls to facilitate drainage and prevent build-up of hydrostatic pressure.
• Equestrian Arenas (Drainage Layer Separation): Separating drainage layers from riding surfaces.
• Green Roofs & Planters: As a filter sheet within the drainage layers.
• General Landscaping: Separating soil from decorative aggregates, mulch, or beneath light-duty artificial grass installations.

Important Note: For applications requiring significant ground stabilisation, load distribution (e.g., standard driveways, roads, heavily trafficked areas, or use on very soft ground), a much heavier grade of geotextile (typically 100gsm upwards, often significantly so, and potentially a woven type for high strength) is essential and should be specified by a qualified engineer.

Installation Guidelines

• Site Preparation:
  • For Trenches (e.g., French Drains): Excavate the trench to the required dimensions and gradient. Ensure trench walls are reasonably stable.
  • For Area Coverage: Prepare the sub-grade by removing sharp objects, large stones, and organic matter. Level as required for the application.
• Laying the Geotextile: Unroll the 80gsm filter membrane into the trench or over the prepared area. Ensure it lines the trench base and sides adequately, or covers the area smoothly without excessive wrinkles or tension. Avoid dragging over sharp objects.
• Overlapping (Lapping): Where sheets of geotextile meet, they must be overlapped to ensure continuous filtration and separation. A lap of at least 300mm is a robust general recommendation for maintaining integrity. Secure laps with ground pegs if necessary, particularly on slopes or in trenches before backfilling.
• Placing Drainage Aggregate/Materials: Carefully place drainage aggregate (e.g., clean gravel or stone) onto or within the geotextile-lined area. If wrapping a pipe, place the pipe, then surround with aggregate, then fold the fabric over the top of the aggregate, ensuring a complete encasement with appropriate overlaps. Avoid dropping aggregate from height directly onto the fabric.
• Backfilling/Covering: Complete the installation by backfilling the trench or covering the fabric with the next specified layer (e.g., soil, paving bedding layer, decorative aggregate). Ensure the fabric is not displaced during this process.

Storage & Handling

• Store rolls horizontally, preferably under cover, to protect from prolonged direct sunlight (UV exposure can degrade polypropylene over time if left uncovered indefinitely before installation).
• Keep away from sharp objects to prevent damage.
• This is a large and potentially heavy roll (approx. 36kg+); ensure adequate manpower for safe handling and transport on site.

Important Considerations

• Not a Primary Weed Barrier (if exposed): While it will block some light, its open pore structure (designed for water flow) means it's not a dedicated weed control fabric if left as the top surface. Weeds can grow in any soil/organic matter that accumulates on top.
• UV Stability: Designed to be covered by soil, aggregate, or other construction layers. It must not be left permanently exposed to sunlight.
• Load Bearing & Stabilisation: This 80gsm fabric has limited tensile strength and is not designed for significant load-bearing or ground stabilisation roles, especially under trafficked areas like most driveways. For such applications, consult specifications for heavier grade geotextiles.
• Aggressive Weeds: Not suitable for controlling invasive rhizomatous weeds like Japanese Knotweed or bamboo; specialist root barrier fabrics are required for these.