Permavoid is a geocellular sub-base replacement system which has been specifically designed and tested to provide stormwater treatment, retention, attenuation or infiltration at shallower depths.

It is ideal for source control and surface water treatment applications, and can easily overcome problematic site conditions such as high water tables, contaminated land and shallow outfalls.The system components can be used individually, or linked together to provide unique and flexible water management solutions.

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What is the Permavoid system?

Permavoid is a geocellular sub-base replacement system, designed to provide shallow stormwater retention, attenuation or infiltration. Permavoid can be used as part of an engineered or soft SuDS solution. It enables designers to offer a source control system incorporating water treatment to manage water where it lands.

Our Permavoid system has been extensively tested over the last decade with Salford and Coventry University, the Transport Research Laboratory and Highways England, to ensure that the system meets the legislative requirements set out by CIRIA, the Environment Agency, SEPA and PPG.

Academic site wide trials include:

  • Transport Research Laboratory – A pilot-scale trial of reservoir pavements for drainage attenuation incorporating Permavoid sub-base replacement system.
  • Coventry University – Assessment and monitoring of the oil retention and performance of the Permaceptor Treatment System.
  • SEPA-Perth Prison – A 2 year field monitoring exercise of macro-pervious pavement and car park installation incorporating Permachannel oil and silt retention devices.


The Permavoid units are suitable for use as a stormwater attenuation and/or infiltration. The system comprises of single, interconnected cells which can be installed in the ground as part of sub-base formation, or above ground as part of roof or podium attenuation systems for source control. Permavoid is suitable for use in a range of applications including residential, industrial estates, car parks, sports pitches, roofs, basements, pedestrian areas and rainwater harvesting.

Key Benefits

  • High strength, high capacity, shallow, sub-base replacement system
  • Stormwater attenuation and/or infiltration system
  • Used as part of a sustainable drainage system (SuDS) scheme to offer stormwater storage at shallow construction depths
  • 100% recyclable
  • Units are manufactured from 100% recycled polypropylene (PP)

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The structural load bearing capacity of the Permavoid units have been tested in accordance with the following European Standard: BS 7533-13:2009. The system’s structural design life expectancy, based upon creep test data (tested in accordance with CIRIA guidelines) is as follows; for lightly loaded areas such as car parks a design life of 50 years is achievable. For areas with prolonged HGV loading a typical design life may only be 25 years, depending on the design of the pavement surfacing and structural layers over the tank.

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All calculations for Permavoid units are based upon site-specific load cases, pavement construction types and thicknesses, soil cover and ground conditions and the suitability must therefore be approved for each project.

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