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PermaSEAL 20 Geodrain Membrane 20m²

£163.00 Ex VAT
£195.60 Inc VAT

A high performance drainage membrane for deck and external waterproofing with 20mm cavity providing highly effective drainage.


High Performance Drainage Geotextile membrane – 20mm

PermaSEAL 20 Geodrain is a high performance twin sheet 20mm universal drainage membrane for external waterproofing, both for vertical below ground application and horizontal above ground applications such as decks, green roofs and hard landscaping.

The PermaSEAL 20 Geodrain features an integrated geotextile layer thermally welded to the studded face. This creates a 20mm cavity which gives the membrane an excellent drainage capacity. Water penetrates the sturdy geotextile layer and enters the 20mm cavities of the dimpled membrane. The geotextile layer filters out small particles to avoid blockages and ensure highly efficient drainage.

Extremely durable and high strength, this drainage membrane is designed to facilitate even load distribution and deal with significant loads. This makes it suitable for driveable decks and patios.   

Uses of PermaSEAL 20 Geodrain Drainage Membrane

Our PermaSEAL drainage membrane is suitable for drainage systems in both horizontal and vertical applications. It can be used in the following applications: 

  • Walkable and drivable deck paving / patios (drainage)
  • Roof gardens & other intensive green roof applications
  • Earth-retaining roofs of underground car parks
  • External waterproofing of basement walls

Installing a PermaSEAL 20 drainage membrane / deck drain membrane

Prior to installation of PermaSEAL 20 apply primary waterproofing to the surface in accordance with the product data sheets to provide a radon, waterproof or gas proof barrier as required. 

Horizontal installation

After your primary waterproofing layer has been applied, starting from the lowest part of the fall of the deck, roll out the PermaSEAL 20 Geodrain with the geotextile facing upwards. Then pull back the Geotextile and reveal the dimpled membrane. Firmly apply a strip of PermaSEAL Jointing Tape or a bead of PM Powerfix to the membrane between the 1st and 2nd row of studs and remove the backing strip. Then unroll the next strip of PermaSEAL 20 Geodrain above the first, overlapping three studs of the first roll and press firmly to create a waterproof seal between membranes.

With rising building elements such as perimeter walls, roof windows etc the drainage membrane should be lapped up at least 15 cm or to the upper edge of the in fill/ substrate.

IMPORTANT NOTE: The surface to be drained should have a gradient of at least 2.2 %. 

You can then add your gravel or vegetation accordingly. 

Vertical installation - external waterproofing

When carrying out external waterproofing of basement walls there are two options for installation. The membrane can be applied in a single roll around the building (subject to a maximum depth of 1.9m). If the depth is above this then the membrane can be installed like wallpaper. Simply cut to size and fix the top of the membrane to the wall with PermaSEAL Quick Plugs. Each sheet should overlap the last by 3 studs and should be sealed with PermaSEAL Jointing Tape or PM Power Fix. In both cases PermaSEAL 20 Geodrain should terminate at the intended ground level.

The membrane should be finished or capped to stop any debris from getting into the cavity. This can be done with lead flashing or similar, a render bellcast.

Remember the geotextile always faces outwards towards the ground.

For more information read our External Waterproofing Guide for basements or browse more external waterproofing membranes.

Permagard - Providing Solutions. Inspiring Confidence.

It is important that you select the correct drainage membrane or green roof membrane to suit your requirements. Our waterproofing membranes function as part of a waterproofing system. Please contact our technical department if you have any questions. Call us on 0117 982 3282.


  • Easy to install
  • 30x higher drainage capacity than required by drainage standard DIN 4095
  • Pressure resistance of 240kN/m2 and is thereby capable of a load of up to 24 tonnes when installed
  • Manageable roll size / weight for one person
  • Long lasting - guaranteed against deterioration for 30 years
  • High compressive strength
  • Tough and durable drainage membrane
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