Greencore Homes Ltd

Description of the Greencore Homes Ltd. Biond closed-panel timber framed building system

The Greencore Homes Ltd. Biond system is intended to be a ‘turnkey’ operation. The system is supplied as structural external wall cassettes for site assembly, with conventional timber frame party/separating walls and internal wall panels. Upper floors and flat roofs may be cross-laminated timber (CLT) panels, metal web joists or timber I-joists. Pitched roofs may be either site installed utilizing standard trussed rafters or prefabricated roof cassettes. The panels are transported to site and assembled upon a prepared sub-structure. The external and internal wall, floor panels and roofs are connected together to provide composite action in accordance with the structural engineer’s fixing specification to meet the requirements of the UK structural codes, and as specifically designed for each structure. External cladding, windows, doors, internal finishes and services are installed on site. The system may be used for single houses, semi-detached, terraced, apartment blocks and commercial premises up to four storeys in height.

Stability of the superstructure is provided by horizontal and vertical diaphragms. Wind loads act on the vertical studs in the external wall panels, which transfer loads to the floor diaphragms immediately above and below. The horizontal diaphragms distribute lateral forces to the walls below, and hence to the foundations.

The timber superstructure at ground level is fixed down to the concrete sub-structure with mechanical anchors at regular centres, which resist shear and uplift forces. Specification of fixings to provide resistance to sliding and over-turning is determined by the engineer according to site exposure.

An accurate sub-structure is required to achieve the required square and vertical tolerances of the erected system. Checks are required to ensure that the level and squareness of the sub-structure are within the stated tolerances.

Limits on Scope

• Maximum four storeys;
• 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;
• 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;
• Greencore Homes Ltd. 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.