Open System Labs Ltd

Description of the Open Systems Lab ‘WikiHouse’ Timber-Based Cassette Building System

The Open Systems Lab ‘WikiHouse’ timber-based cassette building system is an open-source zero-carbon building system that can be shared as code to be digitally manufactured in small, local micro-factories. Open Systems Lab do not manufacture or erect the system themselves. Manufacture, assembly and site installation is by others who must follow the WikiHouse philosophy as specified by Open Systems Lab. Prefabricated wall, floor and roof cassettes are transported to specific site locations and assembled on a pre-prepared base to satisfy the required project configurations. Site operations include installing all necessary project-specific external and internal components, materials, and assemblies, to provide a complete structural shell. External and internal finishes, fixtures, fittings and components are not the responsibility of Open Systems Lab, which is confined to the structural system only.

The system comprises external structural walls, loadbearing internal walls, upper floor and roof cassettes for site assembly. The cassettes are constructed from individual interlocking blocks known as ‘WikiBlocks’ utilising CNC cut 18mm OSB3 or 18mm plywood panels, designed to interlock to form the cassette boxes. The wall, floor and roof cassettes are connected to provide composite action to meet the requirements of the UK structural codes, and as specifically designed for each structure. Windows, doors, external cladding, roof finishes, internal finishes, services, fixtures and fittings are site installed following assembly of the cassettes by others.

Durability Assessment minimum: 60 years

Limits on Scope

• Maximum three storeys subject to structural justification;
• Bottom members of the timber frame must be a minimum 150mm above finished ground level and fully isolated from contact with moisture from the ground or external sources
• Minimum 50mm ventilated and drained cavity behind conventional masonry cladding;
• Minimum 25mm drained and ventilated cavity behind external wall claddings, or as required by the manufacturer; cladding systems relying on pressure equalisation may require a wider back cavity, as required by the designer;
• Where open jointed cladding systems are used, consideration should be given to the use of UV resistant breather membranes, if not protected.
• Some latent defects insurers may require a minimum 15mm ventilated and 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 wall.
• Sub-floor voids must be ventilated to a minimum of 1500mm2/m or 500mm2/m2 of floor area.
• The ground below the floor cassettes in enclosed voids must be sealed against ground moisture, e.g., membrane + 50mm site concrete; where the void is below external ground level, consideration should be given to drainage. Standing water not permitted.
• The system must be designed, manufactured and erected in strict accordance with Open Systems Lab protocols.
• A qualified structural engineer suitably experienced in the design of this type of structure must be engaged for the structural design and analysis.