Ceilings and roofs

BASIX recognises the following roof types:

Flat ceiling and pitched roof

  • Pitched roof (slope > 10°) with roofspace 
  • Flat/horizontal ceiling

Raked ceiling / Pitched or skillion roof

  • Pitched or skillion roof (slope > 10°)
  • Ceiling lining parallel to roof

Flat ceiling / Flat roof

  • Flat roof (slope ≤ 10°)
  • Flat/horizontal ceiling


Tip: Providing roof insulation will reduce your ceiling insulation requirements.


Cross section of a new dwelling underneath an existing dwelling


If your dwelling has another dwelling above (such as a granny flat), you are not required to describe the ceiling and roof type. If the dwelling has part of the ceiling with a dwelling above and part with a roofspace above, describe the ceiling with a roofspace above only.