Platon Double Drain - External Drainage Membrane

Platon Double Drain - External Drainage Membrane

Isola | External Drainage Membranes

Platon Double Drain is a vertical drainage layer for external basement walls and a protection board to primary membranes.

Platon Double Drain consists of an impermeable studded sheet, manufactured from High Density Polyethylene (HDPE) with a Polypropylene filter fabric bonded to the top of the surface of the studs.

Supplied in (W) 2.0M x (L) 15M - (30M²) Rolls.


Platon Double Drain - External Drainage Membrane

Platon Double Drain is a drainage and protection layer comprising a moulded membrane with drainage features on both sides, coupled with a textile filter fleece on the outer face, used on the outside face of basement walls where 'Type A' barrier membranes or 'Type B' integral protection feature as one of the forms of waterproofing.

Platon Double Drain encourages water which is impacting the structure to de-pressurize and percolate down to the maintainable land drain, ideally located on the outside of the slab toe, below basement floor level.

Platon Double Drain is also used to protect and drain horizontal waterproofing across podium decks, terraces etc. where paving or green-roof systems are being laid.

Platon Double Drain is most commonly fitted in vertical strips, held in place along the top edge with Platon X Cramps and Newton GeoStrip Capping Profile.

Benefits & Features:

  • Suitable for use with all Construction Types

  • Drains off water before reaching the Waterproof Coating

  • Easy Handling, Rapid Installation

  • Rugged, Durable Construction with Thermal Insulation Benefits

  • Filtration Layers prevents silting-up

  • High Compressive Strength and Drainage Capacity

  • Combined Drainage and Protection Board

  • Allows Back-filling with Excavated Earth

  • Withstands Stress and Movement in the Background.

Product Uses:

  • Isolate and protect external structure from surround soil

  • Helps relieve hydrostatic pressure from the face of the structure

  • Ideal for retaining walls, podium decks, external tanking and green roof applications.

Technical Data:

Technical Data Result
Materials HDPE & PP Non Woven Fabric
Total Unit Weight 0.59 kg/m²
Drainage Capacity
Max 2.3L/ms
Stud Height 7mm
Colour Black
Resistance To Biological Attack
Does Not Rot or Support Growth
Chemical Resistance
Resistant to All Chemicals in Normal Building Construction
Compressive Strength 180 Kpa
Life Expectancy Lifetime of Structure
Design Considerations

Design Considerations:

  • Build new structures to the requirements of BS 8102:2009. Further guidance is available in CIRIA Report 139 - Water Resisting Basements.

  • Use Waterbars at construction joints as part of an effective multi-staged approach to the waterproofing.

  • Carry out a geotechnical survey to evaluate soil characteristics and groundwater conditions in accordance with BS 8004. Great care should be taken when considering waterproofing that requires the permanent removal of the ground water to be effective. See BS 8102:2009 Section 5 for further guidance.

  • When used as a drainage membrane, Platon Double Drain Membrane should only be used to sloping sites where ground water is diverted around and drained away safely downhill of the structure.

  • The land drain or perforated pipe to the base of an externally applied drainage membrane should be maintainable and graded to an open outlet below the level of the lowest slab. If risk of surcharge exists a pumped back flow protection device should be used. See BS 8102:2009 Section 6.4 for further information.

  • Land drains or perforated pipes should be maintainable. Include accessible jetting ports at regular intervals with at least one jetting port to each elevation.


Substrate Preparation:

Primary structural waterproofing should be in place, this may be a type A liquid or sheet applied membrane or a Type B integral protection if the structure is built from reinforced concrete. The substrate should be clean and free of sharp protrusions.

A fillet or flaunch of concrete or Platinum Fillet Seal should be formed at the toe to wall junction and at the top of the retaining wall to encourage water away from the structure.

Membrane Installation:

Starting at the base of the retaining walls, ensuring that the Platon Double Drain extends out over any foundation toe, hang the membrane in vertical drops with the filter fabric facing outwards and fix with Platon X Cramps along the top edge only at 250mm centres. Alternatively, roll the membrane out sideways, again starting from the base.

NOTE: If a foundation toe protrudes out from the wall, the membrane should be extended over the horizontal section of the toe and down the vertical edge.

Where the next roll / sheet of membrane is to be joined at the vertical edge, carefully peel back the filter fabric from the edge of the sheet to be overlapped by approximately 120mm.

Platon Double Drain does not need to be sealed at joints to function as intended. Platon Sealing Rope can be used if desired, to stabilise multiple sheets and help hold them together until backfilling can commence. The Sealing Rope is laid in a vertical line within the channel between the first and second stud and the overlapping section of membrane is then pressed stud to stud to form a seal down the vertical joint.

Horizontal joints are overlapped in the same manner as above. The uppermost sheet of Platon Double Drain overlaps the bottom one by 120mm to form a weathered junction.

Again, the filter fabric is carefully peeled back from the underlying sheet of membrane at the joining edge to allow a stud to stud overlap. No sealing rope at this horizontal joint is necessary.

The membrane should be terminated at or near external ground level, the exact termination point being determined by the form of build and the type of waterproofing underneath.

Metal flashing may be required to hide and protect the Platon Double Drain / waterproofing combination. At the termination line Newton GeoStrip Capping Profile is fixed using plugs and screws. At the base of the wall, outside the toe of the foundation or slab, a land drain should be installed, surrounded by free draining material and filter fabric. External drainage should be maintainable and reliable.

Back-filling should be carried out in layers, using a free draining material, with care being taken to avoid damaging the Double Drain by piercing it and the underlying waterproofing or pulling it off the wall.

Data Sheets

Technical Data Sheet

System Platon Installation Manual

Platon Cavity Drain Systems Brochure

CE Marking Certificate

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