Oldroyd Gtx is a 2 m × 15 m studded polypropylene cavity drainage membrane with geotextile filter fleece - sometimes referred to as a 'fin drain', a 'geocomposite membrane' or a 'geocomposite.'

Oldroyd Gtx is widely used to act as a secondary drainage layer for basement waterproofing. The primary waterproofing is provided by the structure itself (e.g. concrete to BS8007) or by a tanking slurry or membrane (BS8012 type A). In these situations, applying Oldroyd Gtx to the external walls of the basement has the advantage of reducing pressure on the primary waterproofing system as water pressure is diverted away from the basement walls.

Oldroyd Gtx also has applications in providing drainage on horizontal surfaces (e.g driveways, patios) and ground gas mitigation.

Consideration should also be given to Oldroyd Gtx10 (higher compressive strength and flow capaicty) and Oldroyd Gtx20 (higher flow capacity).