11.3.10 Junctions and interfaces
Junctions and interfaces shall be suitably detailed, built to appropriate tolerances and provide satisfactory performance.
The use of volumetric units, particularly where finished linings or claddings are installed will introduce junctions and interfaces between adjoining units that are not common in traditional construction.
The junctions of volumetric units should be designed with appropriate tolerances to avoid excessive deviation:
- to external faces of adjacent units, which may impact cavity widths, installation of insulation and cladding as well as performance of cavity barriers or fire-stopping
- to internal faces of adjacent units, which may impact continuity of acoustic or fire-resisting linings or installation and fit of surrounding construction (eg staircases).
Spatial tolerances are critical for the performance of joints, details, and interfaces. The design should:
- include dimensions and the permissible deviation clearly indicated in the System Manual and on relevant drawings
- allow for adjustability to accommodate the tolerances for manufactured units and range of deviation in site construction in the form of levelling bolts, bracket systems and detailing allowing horizontal and vertical adjustment.
The manufacturer and designer should consider:
- guidance on jointing methods for structures, claddings, openings, and services passing through building elements given in BS 6093
- undertaking of mock-ups or trials to ensure satisfactory fit and tolerances can be achieved.
Foundations
Foundations should be installed to tolerances in accordance with the System Manual. The foundation tolerances should consider:
- level of foundation
- straightness of foundations
- dimensional tolerance
- level between foundation and substructure brickwork
- squareness of foundations.
Floors
Interfaces of floors at unit junctions should be designed to achieve necessary tolerances to allow installation of floor coverings. Interfaces of floor decking may either be designed as a butt joint or by using a transition piece to accommodate minor tolerances between decking finishes.
Floor interfaces should:
- have a nominal 3mm gap at decking joints
- filled with an appropriate gap filler or covered with a cover strip
- be kept clear of debris
- not exceed 2mm level difference between floor decking at any position.
Last updated: 2nd January 2025