Geotextile Membranes

What geotextile membrane is used for

Geotextile is used wherever stone sits on soil and the two must not mix, and the job decides which fabric goes in, where it sits and which way water has to move through it.

Site access roads, haul routes and hardstanding

On a site road or haul route, the geotextile goes on the stripped formation directly under the sub-base, and its work is to keep the stone clean of the clay beneath while lorries and plant run over it. The same build-up applies to compounds, piling and crane platforms and laydown areas, where a contaminated base would have to be dug out and replaced.

Driveways, footpaths, patios and car parks

Under a driveway, footpath, patio or car park, the fabric sits between the subsoil and the sub-base, below any bedding layer for paving or block. A woven separator is the usual choice under gravel drives and car parks that take vehicles, while paths and patios that carry only foot traffic can go on a lighter grade or a non-woven fabric.

French drains, soakaways and percolation areas

Drainage work turns the choice towards non-woven fabric, because water has to pass freely through the layer while silt stays out of the stone. In a French drain or filter drain, the fabric lines the trench and wraps over the top of the stone so the pipe and the voids stay clear, and a soakaway is wrapped in the same way around its stone or crates. In a percolation area, the fabric goes over the stone around the distribution pipes, so topsoil backfilled above cannot wash down into it. Where a drainage layer has to carry water sideways, for example behind a retaining wall, geocomposite drainage does the job in a single product.

Riverbanks and coastal erosion works

On riverbanks and coastlines, the geotextile goes between the bank and the rock or stone that protects it, holding the soil in place while water moves through, so fines are not washed out from behind the armour. The woven reinforcement fabric is made for this work. For slopes, silt control and runoff on open sites, the erosion and sediment control range covers the surface measures.

Geotextile grades and roll sizes

Once the type is settled, the order comes down to the grade within the family and the size of roll the job can use.

Choosing a grade

Terram, the Lotrak drainage fabric and the Lotrak R reinforcement fabric each run from lighter to heavier grades. Within a family, choose a heavier grade for heavier traffic, for coarse or angular fill that could puncture a lighter fabric, and for soft or wet ground where the fabric is stretched as stone is placed. A lighter grade is enough for footpaths, patios and drain wraps, where the load is light and the fill is finer. Where a road or platform has an engineer's design, order the grade it specifies.

Roll widths and lengths

Short trade rolls of woven and non-woven fabric suit paths, patios and drain runs, where a full roll would leave offcuts. For roads, car parks and platforms, full site rolls run up to 100 m long and over 5 m wide, so each roll covers a large area with fewer joints and fewer overlaps to set out.