Fildrain – Highway Edge Drains

Fildrain drainage geocomposites are a cost effective alternative to traditional stone drainage for highway edge drains and concrete central reservation drainage. The geocomposite collects and channels liquids to a carrier pipe for transportation to a suitable discharge point along the highway.

Fildrain has a unique drainage core that collects and channels water from the road to a carrier pipe for transportation to a suitable discharge point.


  • Edge of carriageway fin drain drainage system to DFT HCD figure F18
  • Drainage to concrete channels to DFT HCD figure F21
  • Cost effective, carbon saving alternative to granular French drains
  • Combined surface and sub-surface drainage


  • BBA HAPAS Approved
  • High water flows compared to traditional drainage stone
  • Allows water flow in all directions
  • Space saving, narrow trench requirement
  • Re-use of site won excavated material
  • Reduction or elimination of drainage stone & haulage requirements

Fildrain fin drains provide a very high flow capacity, many times that of traditional crushed stone (specific data is available). This is due to the unique open structure created by the dimpled construction which allows un-hindered water flow.

ABG Fildrain fin drain geocomposites, for highway edge and central reservation concrete channel drains, channel water to a discharge drainage pipe, providing an ideal alternative to the construction of ‘traditional’ narrow Type 8stone filter drains, saving time, carbon and money on highway and railway construction projects.

The Fildrain Types range is designed in accordance with the Department for Transport Volume 1 – Specification for Highways Works Series 500, and are fin drains as defined in the Manual of Contract Documents for Highway Work (MCHW) Volume 3 Drawing nos. F18 and F21. They also conform to the Transport Infrastructure Ireland (TII) Specification for Road Works Series 500.

Fildrain Type 6

ABG Fildrain Type 6 highway edge fin drain provides vertical drainage on both sides, whilst acting as a barrier to protect the sub-base from inundation from the road verge. Fildrain Type 6 fin drain system is a double cuspated drainage geocomposite fully, wrapped with a filter geotextile and an integral pipe sleeve. The Fildrain geocomposite is laid alongside the trench, threaded with perforated pipe and lowered into a narrow trench before backfilling and compacting the excavated soil back into the trench adjacent to the drain. The surface is then covered with soil or a shallow apron of stone. ABG Fildrain Type 6 incorporates a geotextile sleeve to accept a 110mm OD carrier pipe in accordance with specification clause requirements. For larger diameter pipes Fildrain 7DW[P] or 7DW[F] are applicable.

Fildrain Type 10

The ABG Fildrain Type 10 fin drain, a BBA certified system, is designed for use underneath trapezoidal concrete channel drains. Benefits of Type 10 fin drain include the strong but flexible HDPE cuspated core which provides a regulated surface and creates a keying effect for the concrete to aid slip forming. The well bonded geotextile and dimpled surface gives a high friction surface to the underside to prevent movement.

The ABG Fildrain Type 10 is compatible with the ABG Fildrain Type 5, 6 and 7 highway edge fin drains on one side of the channel and allows the choice of two alternative corner details as illustrated in HCD F21, shown below.

Concrete can be cast into the back of the Fildrain Type 10 Drainage Geocomposite. View an installation video below:

Fildrain Type 7

The ABG Fildrain Type 7 fin drain is a BBA certified highway edge findrain system that incorporates a slit solid pipe with a sealed invert. Fildrain 7DW is a findrain with a similar configuration that can be used with pipes of differing configurations, or without a pipe depending on the application.

Fildrain Type 5

The ABG Fildrain Type 5 is a BBA certified fin drain system, designed for highway edge drainage. The Fildrain Type 5 Fin Drain geocomposite strip allows the excavated material to be simply backfilled into the trench and requires no import of clean aggregate. At the end of each run, a fitting is used to connect to the outfall pipe. Type 5 highway edge fin drain draiange system is a low cost system, with low embedded carbon which is suitable for manual or mechanical installation. Fildrain 12SW and 25SW are of a similar configuration, but are typically supplied in shallow strips for use alongside permeable paving.

Traditional French Drain Construction

Consists of an excavated trench, infilled with free-draining aggregate. This type of construction may require off-site material import and the removal of excavated materials. Trench width is typically 300mm to 500mm, a high cost option with a large carbon footprint.

Typical Client Profile

  • Higways Contractors
  • Highway Engineers
  • Rail Engineers

DfT Edge of Pavement Drains (Fin Drains and Narrow Filter Drains) – Drawing F18 (Highways Construction Manual)

NRA Edge of Pavement Drains (Fin Drains and Narrow Filter Drains) – Drawing RCD/500/40

Highway Edge Drainage – Carbon Footprint Saving

The use of ABG’s Fildrain Highway Edge Fin Drain Drainage Geocomposites can save up to 74% on carbon footprint when compared with traditional granular soil drainage methods:

Click to read the full carbon footprint assessment

Case studies

Additional information

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