GEOfabrics Cuspates are a polymeric sheet material that have been vacuum formed into either a stud or cup to provide a void space for the passage of either a liquid or a gas. They are available in a range of heights to suit design requirements.

It is common for a cuspate to be used as a component in a Geocomposite, in conjunction with a geotextile filter. They are commonly used in gas protection systems, cut off walls around contaminated land, at the rear of bridge abutments and retaining walls, and around buried structures.


GEOfabrics manufacture Cuspates from optimum quality high density polyethylene or polypropylene, which is extruded into a range of different thickness membranes.

The sheet is formed in an extrusion process, whereby semi-molten polymer is extruded through a flat die, with normal thicknesses from 0.4 to 2mm. These impermeable membranes are vacuum formed into geocuspated cores between 6mm and 40mm thick, depending on the mechanical and hydraulic properties required.

Vacuum forming is a simplified version of thermoforming, whereby a sheet of plastic is heated to a forming temperature, stretched onto a single-surface mould, and forced against the mould by a vacuum (suction of air).

An alternative to Vacuum forming involves a continuous process where semi-molten polymer is formed between two corresponding rollers with male and female forming points. This process allows us to control quality from polymer source through to finished cuspated drainage core.

Typical uses are: 

  • Green Roof systems
  • Horizontal drainage systems
  • Vertical Drainage systems
  • Gas Venting

GEOfabrics’ Cuspates are named in accordance with the thickness of the material; e.g. CO20 = 20mm thick. GEOfabrics’ cupates are also supplied as composites with a geotextile filter bonded to either one side (FC) or both sides (FCF)

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