One of the important facts about Geotextile protective underlay

Geotextile, as described in Wikipedia, is a permeable fabric which when associated with soil has the ability to separate, filter, reinforce, protect and drain. Geotextile comes in three basic forms: woven, needle punched and heat bonded. Geotextile is used for a wide range of civil engineering application types such as roads, retaining structures, dams, reservoirs and ground bank protection. It is used to improve soil strength and prevent erosion.

In the water containment industry, Geotextile is used as a protective layer between the soil and the liner to contain water in a dam, pond, reservoir or lake. It comes in various thicknesses but for the best, most reliable protection a Geotextile thickness of 150gsm for residential garden ponds and 250gsm for large ponds and lakes is ideal.

Some pond builders consider using carpets but woollen ones will rot over time plus the hard backing means it won't mould readily over the contours of the substrate.

What is less well known about geotextile material is that it can also be used as a protective pond liner overlay – and there are several reasons why this would be an advantage. One example of where you would install an overlay is on top of the lining around the edge of a pond where the pond liner rises out of the water and lies on top of the surrounding soil or collar. Here an additional over-layer of geotextile is placed before the stones or slabs are added to create the pond edging. Similarly, for ponds that feature an underwater shelf or platform for shallow water plants, those areas too should use a protective overlay.  The presence of an overlay can also provide some protection against the sharp claws of pet dogs or cats – and even the stab of a heron’s beak.

Place it underneath stone features, plant containers, gravel or pebbled pond floor - the whole floor of a pond can be given a protective overlay with geotextile material. As well as protecting the pond liner, the textured surface of the fabric will discourage pebbles and other features sliding if the floor is not level.

Why quality of Geotextile protective underlay matters?

Ground surface preparation is very important prior to the installation of a pond liner for applications from garden ponds to lakes and reservoirs. This is important to reduce any possible damage to the pond liner.

The substrate should be free of rocks, stones, roots, sharp objects and any sharp or pointy debris. The surface needs to provide a firm foundation and should also be free of standing water or excess moisture. Geotextile protective underlay is highly recommended even though the surface has been thoroughly prepared. Quality matters because the thicker and more durable this felt-like layer, the greater the protection over time - against ground movement and the pressure of water bearing down on the pond liner. 

Geotextile 150 and 250gsm (gsm = grams per square meter) grey protective pond underlay is a mechanically bonded polypropylene needle-punched material that offers the following features: 

• tough relative to some brands available on the market

• offers exceptionally high performance 

• provides a highly effective protective barrier between substrate and pond liner

• heavy duty underlay 250gsm is designed for installation beneath all pond liners to help protect from penetration by sharp stones, roots and any sharp objects pushed up through ground movement

• reduces excessive localised stretching of the pond liner when ground settlement occurs over time. 

• for small garden ponds Geotextile 150gsm (gsm = grams per square meter) is sufficient

Geotextile protective underlay is inexpensive relative to the cost of building a pond or lake so a small price for a life-time of protection.