Structural Drainage – Basements & Podiums

Structural drainage covers any drainage system or product which controls groundwater, helps remove surface water or alleviates hydrostatic pressure.

Drenflex, Deckdrain and Roofdrain geocomposites provide a high flow drainage path in a thin and light-weight layer for modern podium deck build-ups and to relieve pore water pressure from the back of buried building structures. They represent a carbon saving and easier to install alternative to hollow concrete blocks for wall drainage and crushed stone layers beneath paved areas. High CBR puncture resistance also offers additional protection to the waterproofing in both situations.

Typical applications

  • Basement waterproofing
  • Buried structure waterproofing
  • Carbon saving alternative to French drains with filter stone and pipe
  • Cavity drainage / membrane
  • Waterproofing protection board


  • Thin drainage layer maximises internal space
  • Easy to handle & quick to install
  • Cost effective
  • Higher in-plane flow than crushed stone
  • Protects the waterproofing
  • Huge carbon saving compared to installation of hollow concrete blocks

Unique core design withstands compressive loads from backfill operations

Drenflex and Deckdrain are supplied in rolls, available in standard dimensions of 1.1m wide x 50m long or 2.2m wide x 25m long to enable quick installation and coverage rates. A range of core drainage thicknesses are also available, depending on the in-plane flow performance required and the volume of excess pore water pressure to be drained.

Basement wall drainage
The 4mm or 6mm drainage core size is the most commonly specified for the lining of basement walls in building applications where waterproof protection is required for below ground structures.

External basement walls
The aligned flow paths of the cuspated drainage core gives high flow performance in all directions and replaces the need for heavy concrete block drainage.

Podium Landscaping & Drainage

Many new buildings incorporate landscaped amenity areas above basement or car park areas. These podium decks can vary from lawn, planter & paved amenity spaces; to additional areas for access or car parking. These are often large, waterproofed decks with minimal falls which makes drainage a key design parameter. Deckdrain sub-surface drainage layer / geocomposite offers an effective and reliable drainage system for podium decks of all sizes, whilst also providing additional protection to the waterproofing layer below.
Geosynthetics used for structural drainage with buried structures
In addition to drainage of standing water from waterproofed decks of all sizes, Deckdrain’s high CBR puncture resistance protects the waterproofing from backfilling forces and root penetration, thus extending the performance and life of the system.

High compressive strength drainage cores
The Roofdrain 60 geocomposite offers a high compressive strength and enables a shallower drainage design for podium deck structures. Using a structural geocomposite drainage core in this application means the installation time and amount of drainage stone required can be significantly reduced.






The 60mm HDPE core provides an uninterrupted drainage void, allowing water to flow in all directions across the whole installed area. The cuspates can be interlocked to connect adjoining panels and can be stepped to achieve a tiered installation. Applications include block and permeable paving, with the 60mm deep Roofdrain core supplied in roll format to enable fast installation over large areas.


The storage cuspates are typically filled with pea gravel to provide a rigid sub-base and the upper side of the drainage core includes perforations to allow water to percolate through to the channels on the under side.

Project Attenuation Calculations

Submit your project design request via our Design Solutions form.

Additional information

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