6.4 Timber and concrete upper floors

6.4.12 Joists connected to steel

Joists shall be suitably connected to steelwork.

Solid timber joists

Where connected to steel beams, solid timber joists should:

  • be deep enough to be notched
  • have 12mm top and 2mm bottom projections to allow for timber shrinkage
  • be provided with strutting to prevent rotation.

I-joists

Where connected to steel beams, I-joists should not be notched at the flange, and should:

  • bear directly into the steel beam where the bearing is more than 45mm. Strutting, (noggings 38mm x thickness of flange) should be provided at the top and bottom flanges, or
  • have blocking fixed to the steel beam to enable the I-joists to be face fixed using joist hangers. Strutting is not required when hangers the full depth of the joist are used to face fix joists to the blocking.

Metal web joists

Where connected to steel beams, metal web joists should not be notched at the flange, and should:

  • bear directly into the bottom flange of the steel beam where the bearing is more than 75mm. There should be timber uprights between the flanges and 38mm x 97mm noggings between the uprights
  • where the bearing is less than 75mm, the joist can be supported on the top flange with the bottom flange fixed to timber blocking supported inside the steel beam.

Last updated: 2nd January 2024

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