Timber and concrete upper floors

6.4.17Multiple joists

Multiple joists shall be securely fixed together.

Joists can be doubled or tripled up to provide additional support, e.g. for lightweight partitions or to form trimmers. The design should specify how the joists are fixed together and be in accordance with manufacturer’s recommendations.

When securing joists:

  • fixings should be in accordance with the engineer’s specification and should be checked before the ceiling is fixed, including the tightness of bolts
  • toothed plate, split ring and shear plate connectors should be provided where required
  • washers or single-faced connectors should be used with bolts
  • ensure that timber is not damaged by over-tightening.