11.3.7 Differential movement
Buildings formed using volumetric systems shall account for differential movement between the frame and other building elements or supporting structures.
Where volumetric units connect to surrounding construction and differential vertical movement is expected, consideration should be given to:
- the design of joint details and accommodation of differing floor levels at thresholds, staircases and lift shaft enclosures
- service entries and risers
- design and provision of suitable weather resistant and durable joints
- interface of self-supporting cladding and cladding attached to the unit
- design of connection brackets, anchors, and ties to accommodate movement.
Timber frame volumetric
Where the primary structure of volumetric units is timber, it will shrink as the timber dries out, reducing the overall height. In some cases the expected shrinkage can be greater than that of traditional platform framed timber buildings due to the form of construction. The extent of the differential movement increases with the number of storeys, and the design should allow for differential movement between the volumetric units and other parts of the construction, including:
- door and window openings
- eaves and verges
- balconies (including Juliet balconies)
- service entries, risers and fixed vertical external services
- openings for drive throughs
- staircases and lift shaft enclosures (where they are not timber framed)
- the interface of the timber volumetric unit with any other construction at each floor level where cladding is fixed to the unit.
For timber frame volumetric structures the shrinkage and associated gap sizes to accommodate differential settlement should be subject to specialist calculation.
Where claddings are factory installed and supported by the volumetric unit, consideration should be given to interfaces with self-supporting cladding.
Refer to Clause 6.2.8 for guidance on how to accommodate differential movement in traditional platform timber frame construction.
Light steel frame volumetric
The design for differential movement in light steel frame volumetric structures should be in accordance with the System Manual. Also see Clauses 6.10.20 and 6.10.21.
Last updated: 2nd January 2025