Skip to main content



BASIX recognises the following floor types:

  • Concrete slab-on-ground
    Concrete slab laid directly on compacted soil, sand or gravel with no airspace below.
  • Suspended floor with open subfloor
    Open subfloor means that the airspace under the floor is unenclosed between ground and floor level, or enclosed by walls which have more than the required subfloor vents. Nominate this type if you have a carport below.
  • Suspended floor with enclosed subfloor
    Enclosed subfloor means that the airspace under the floor is enclosed between ground and floor level by walls which have only the required subfloor vents.
  • Internal floor above habitable rooms or mezzanine
    Nominate this type if the floor is a mezzanine, is above habitable rooms in the same dwelling, or is above another dwelling.
  • Suspended floor above garage
    Nominate this type if you have a carpark or garage below. This type of floor may still require insulation as there can be significant heat transfer between the garage and the dwelling.

Be sure to nominate all of the floor types in your development. For example, for a combination slab-on-ground and suspended floor, select both slab-on-ground and the appropriate suspended floor option.

Prior to 1 July 2017, BASIX allowed a concession to dwellings with a suspended floor on certain constrained sites, such as a steeply sloping site, flood-prone area or mine subsidence area. This concession is no longer available. More information on the suspended floor concession is available here.

Last updated: 26/09/2023