Portakabin Limited

Description of the Portakabin Limited Alta Composite Steel Modular Volumetric Building System

The Portakabin Limited Alta system is intended to be a ‘turnkey’ operation, that is, the shell of the building including external and internal finishes will be designed, manufactured and erected by Portakabin Limited. The system is intended primarily for transitional housing relief being provided by Local Authorities as an alternative to temporary hostel and hotel accommodation. Portakabin Limited always remains the owner and leases the system to the relevant authority. As the system is fully demountable, at the end of a lease period, modules will be returned to an authorised Portakabin Limited hire and refurbishment centre, where any necessary repairs and refurbishment will be carried out to bring the modules back up to original condition.

The 95% externally and internally completed units are transported to site, erected on a pre-prepared sub-structure and structurally interconnected to provide composite action using bolts, in accordance with the engineer’s fixing specification, to meet the requirements of the UK structural codes. Site works are limited to completing structural, finishes and services connections. The
system is intended for residential buildings up to three storeys in height, typically arranged in semi-detached and terraced configuration, in accordance within the Alta system’s published limitations. The modules must be stacked vertically in the same orientation – side-to-side or end-to-end orientation is preferred as it is quicker to install and simplifies the connections. Side to end is an option but requires additional channel and vertical seals installed; also complicates floor infill and column casings. Modules may be stepped but requires more complex weatherproofing. Modules can incorporate internal staircases. Joints between modules are sealed with flexible EPDM seals.

Limits on the scope of this assessment

• Maximum three storeys;
• Bottom members of the frame must be fully isolated from contact with moisture from the ground and external sources;
• Thermal checks must be undertaken to ensure that there is no risk of interstitial condensation and/or cold bridging which may impact the durability of the modules;
• Portakabin Limited must be contracted for the design, manufacture, supply and erection of the structure;
• System must be maintained in accordance with Portakabin Limited’s recommendations;
• A qualified structural engineer suitably experienced in the design of this type of structure must be engaged for the structural design and analysis.

Durability Assessment: Minimum 60 Years