Newsletter 2: Joists

Newsletter 2: Joists

What lies under the floor is just as important as the floor itself.

To ensure a high quality and great performing floor, it is imperative that as much thought and care that goes into the floor, also goes into the subfloor.

Apart from the subfloor needing to be as flat as possible and set to the correct height, it must also have the correct moisture content and be designed in a way as to give the best possible support to the flooring.


Important things to consider when designing or building a subfloor


  • Subfloor ventilation – A poorly ventilated subfloor can have a disastrous effect on a timber floor.
  • Joist direction – flooring should always be run at 90° to floor joists. This will avoid a wave like appearance due to the particleboard sagging and inconsistent pressure being put on a single joist instead of spreading the load across many joists.
  • Fixing of subfloor sheeting to joists – subfloor sheeting should always be screwed and glued with elastomeric adhesive. Timber floors cause up to 250KG/sqm of uplift when they expand due to an ingress of moisture. This pressure will tear incorrectly fixed subfloor sheeting from the joists and deform poorly designed subfloor framing.
  • Junctions between concrete slabs and joists – It is imperative that the subfloor sheeting spans these junctions, so that any movement of the joists is not transferred to the flooring and the subfloor sheeting keeps the junction flat and together.