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STAKKAbox™ Fortress

The STAKKAbox™ Fortress range of network access chamber systems is strong yet lightweight, structural, scalable, and suitable for use within multiple sector applications. The Fortress chamber system has been designed to significantly reduce the costs of network access chamber installations.

With its twinwall design and individual sections, the Fortress solution is lightweight, meaning it can be manually lifted and stacked one on top of the other to reach the specified depth required.

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Features & Benefits

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 to overbuild over existing networks, Introduce duct entries for cable entry and for 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 as well as allowing flexibility in delivery and installation.


Due to the sectional, twinwall design all Fortress 150mm sections are under 25kg in weight, making it suitable for a single person lift under manual handling regulations.


STAKKAbox™ Fortress is manufactured in nitrogen foamed High-Density Polyethylene (HDPE), of which up to 70% is recycled material. HDPE possesses excellent strength to weight properties.

Chemical Resistance

HDPE outperforms traditional construction methods for chemical resistance during its buried life, resulting in a product that offers a longer install life.

How it's Built

STAKKAbox™ Fortress chambers are built by combining four interlocking sidewall pieces to form a chamber ring section. These ring sections are 150mm deep and are then stacked on top of each other to reach the specified depth required. Providing contractors with a means of constructing access chambers quickly and inexpensively while offering improved build quality, reduced defects, and enhanced site safety performance. When constructing an ULTIMA Connect chamber, you must remember to start with a full ring section of either left or right corner pieces. You can then build up from this using alternative corner pieces per ring section until the specified depth of the chamber is reached.



STAKKAbox™ Fortress is manufactured in nitrogen-foamed High Density Polyethylene (HDPE), of which up to 90% is recycled material.

HDPE possesses excellent strength to weight properties, and its twinwall design gives it strength, with Fortress being extensively tested to ensure that it meets loading requirements up to D400 in a variety of installation environments.

Available Sizes

Available Sizes

Fortress chamber sizes have been designed to be reflective of the most commonly used access chamber sizes. Fortress chambers are constructed from standard component parts, allowing for greater flexibility during transportation and installation.

Download our product size guide for chambers for more details on available sizes


Using Fortress access chambers can help to save even more time, with their adaptability to onsite conditions with standard tools to overbuild or bench existing network utilities, introduce duct entries for cable entry, and allow for top-section level adjustment.

Their range of accessories for installers to simply place, connect up tubes or ducts, backfill, and walk away makes them the ideal solution for a range of installation environments.

Load Rating

Load Rating

STAKKAbox™ Fortress is suitable for meeting installation environments rated to D400 under EN124.

Ideal for areas imposing wheel loads, such as carriageways and roads open to commercial vehicles, whilst still enabling both scalability and adaptability to varying underground utilities.


STAKKAbox™ Fortress can be supplied with the following accessories:

Base Sections

Base Sections

We extrude 100% recycled Low Density Polyethylene chamber bases to suit any chamber size. These are securely fitted to the bottom ring section of a chamber to provide a clean easy finish to the floor of the chamber.

X-TRAS™ Range

X-TRAS™ Range

Using Cubis access chamber systems accessories can help save even more time. Our chamber options & accessories range allows installers to simply place, connect up tubes or ducts, backfill and walk away.

AX-S™ Covers

AX-S™ Covers

The Cubis AX-S™ range of access covers provide customers with a complete underground network access system as they are designed and manufactured from a range of materials to complement our chamber ranges.

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