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Fortress 1 & 2
Fortress 1 & 2
FORTRESS (Photo) (1)
FORTRESS (Photo) (3)

STAKKAbox™ Fortress is a range of modular and structural preformed access chambers, suitable for use in carriageway and footway environments (in accordance with Cubis’ installation guidelines). 

The system provides contractors with a means of constructing access chambers quickly and inexpensively, whilst offering improved build quality, reduced defects and enhanced site safety performance.

The Fortress system is moulded in HDPE and possesses excellent strength to weight properties. Each section is ribbed internally to improve loading performance.

Using the Fortress system, complete chambers can be constructed from excavation to reinstatement in less than one hour.

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  • Fast and easy to install
    STAKKAbox™ chambers are significantly faster to install than conventional alternatives, with complete installations typically taking up to one hour. This results in reduced costs for the installer. No specialist equipment or plant is required in order to install the chamber and there is no need for specialist box builders. 
  • Sectional & twin wall design
    Chambers are built to required depth by adding 150mm sections. Due to the twinwall design, individual sections are light meaning they can be manually lifted. Each access chamber possesses vertical and horizontal ribs,  resulting in a product that is strong vertically and on the sidewall. Most installations do not require specialist backfills, reducing installation costs.
  • Flexible during installation
    Chambers can be adapted to suit on-site conditions with standard tools
    • Overbuild over existing networks
    • Introduce duct entries for cable entry. 
    • Top-section fine adjustment
  • Smooth outer walls with lip to ‘key in’
    Gaps in the outer wall will negatively impact the effectiveness of compaction around the chamber. STAKKAbox™ chambers have smooth outer walls and an outer lip which keys into the backfill.
  • Flat pack option
    Fortress can be supplied in 'flat pack' format to make shipping more efficient.

STAKKAbox™ Fortress is commonly used for the following applications:

Highways (outside UK)

  • Motorway Communications


Rail (outside UK)

  • Telecommunications


Power & Energy

  • Low Voltage power cable link boxes



  • Jointing chambers (Virgin Media, local networks)



  • Valve chambers
  • Telemetry chambers

STAKKAbox™ Fortress is suitable for installation in environments rated to E600 under EN124, in accordance with Cubis' installation guidelines.

STAKKAbox™ Fortress is manufactured in nitrogen-foamed High Density Polyethylene, of which up to 70% is recycled material

Benefits of HDPE:

  • Excellent chemical resistance to ethanol, acetone, diesel etc.
  • Unaffected by sulfate ground conditions.
  • Recyclable
  • Robust - no breakage waste
  • Completely impervious to water
  • Nitrogen injection creates cellular core (CFC free)
  • High strength to weight ratio
  • High stiffness to weight ratio
  • Easy to cut for duct entries

Chamber Accessories

Access chambers can be pre-fitted with the following accessories:

  • Duct Entry
  • Cable Management
  • Steps

For more information, please visit the access chamber accessories page.

Base sections

Standard Base

Access chambers can be supplied with a base section, manufactured in ABS or LDPE. These are securely fitted to the bottom ring section of a chamber to provide a clean easy finish to the floor of the chamber. There is no requirement to 'float' a floor on site and the floor prevents vegetation and silt from entering.

Available sizes

Clear Opening Profile External Depth
445mm x 445mm A 550mm x 550mm 150mm
610mm x 445mm A 715mm x 550mm 150mm
610mm x 610mm A 715mm x 715mm 150mm
675mm x 675mm A 780mm x 780mm 150mm
915mm x 445mm A 1020mm x 550mm 150mm
915mm x 610mm A 1020mm x 715mm 150mm
915mm x 915mm A 1020mm x 1020mm 150mm
1220mm x 675mm A 1325mm x 780mm 150mm
1220mm x 1220mm A 1325mm x 1325mm 150mm
1310mm x 610mm B 1480mm x 901mm 150mm

Download our product size guide for more information on available sizes.

Related Products

Related Case Studies

fortress install jpeg STAKKAbox™ Fortress Trial: NSW - Australia

Cubis Systems recently trialed the STAKKAbox™ Fortress and its application capabilities to Australian rail networks.