Rockmount Construction Ltd

Description of the Rockmount Group Panelised Light Gauge Steel Frame Building System

Manufactured in the United Kingdom by the Rockmount Group, and its approved sub-contractors, the factory assembled wall, floor and roof panel cassettes comprising the steel framing are transported to site and assembled in sequence on a prepared sub-structure. Floor cassettes are pre-boarded in the factory and external wall panels are sheathed externally on site. The foundations and sub-structure are site specific and constructed by others, and are not part of Rockmount Group’s remit. External wall claddings, insulation, internal finishes, fixtures, fittings and services are not part of Rockmount Group’s remit.

The structural elements are structurally interconnected to provide composite action in accordance with the requirements of the UK structural codes and as specifically designed for each structure. Applied cladding must not exceed the loading limits for the structures. Rockmount Group must agree the proposed finishes to ensure that structural and environmental factors will not adversely affect the durability of the system.

The system may be used to form individual site assembled 2D loadbearing panels, or as infill to a primary structure constructed by others. The system comprises a range of S390GD + Z275, S450GD+ Z275, or S600GD + Z275 galvanised lightweight steel sections produced to BS EN 10326. U and C sections, typically 63, 75, 100, 150, 200, 250 and 300mm deep and 1.2mm to 2.5mm thick, form the external and internal walls, upper floors and roof panels – size and thickness depending on structural requirements. The system construction is based upon the ‘warm frame’ principle where the majority of the insulation is placed outside the structural frame. This is installed on site by others. Wall panels are constructed with C section top and bottom rails with C section studs of size and spacing commensurate with the structural design. Upper floor and roof cassettes may be formed of C joists or lattice joists constructed of C sections, depending on span/loading requirements.

Limits on the scope

• Maximum six storeys for loadbearing frames subject to structural analysis (with the incorporation of hot-rolled steelwork to achieve structural design parameters);
• Panels in contact with the foundations/sub-structure must be fully isolated from contact with moisture from the ground and external sources, and be a minimum 150mm above finished ground level;
• Where light gauge steel framing is used for ground floor construction, the ground below the floor must be sealed to prevent moisture entering the void, such as a membrane overlaid with 50mm oversite concrete, in accordance with the recommendations of Steel Construction Institute publication P262. Where voids are below external ground level, consideration should be given to void drainage. Standing water not permitted;
• Where a light gauge steel frame ground floor occurs over a void next to the ground, the void must be cross-ventilated to a minimum standard of 1500mm2 /linear metre, or 500mm2/m2 of floor area;
• Minimum 50mm ventilated and drained cavity behind conventional masonry cladding;
• Minimum 25mm drained cavity behind external wall claddings, or as required by the system designer [open jointed and rainscreen systems utilising pressure equalisation may require a wider cavity to be effective];
• Some latent defects insurers may require a minimum 15mm drained cavity behind insulated render and insulated brick slip systems, in all exposure areas. This is intended to minimise the risk of water penetration damaging the structural frame, particularly at openings in the walls;
• 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 panels;
Durability Assessment Report Template
• Rockmount Group must be contracted for the design, manufacture, supply and erection of the structure;
• A qualified structural engineer suitably experienced in the design of this type of structure must be engaged for the structural design and analysis.