What’s the difference between Class 1 and 2 Dwellings? Here are the basics.

Class 1a Dwelling Units
Class 1a Dwelling units have a separating wall between each dwelling unit that extends continuously from the ground to the underside of the roof of the units.

Class 1 buildings cannot be built on top of each other, and each is totally independent of the adjoining class 1a except they share a separating wall.

Please note I did not use the term fire wall. Separating walls function as fire separation, however, they are not fire walls as defined in the BCA Volume 1.

Class 2 Dwelling Units
Class 2 dwelling units are not independent of each other like Class 1a buildings. They can share entries, hallways and roof space, or be built on top of each other.

In a Class 2 Dwelling, the space contained within the floor, walls and ceiling of the dwelling unit, is separated from the other common parts of the building or other Class 2 Dwellings. The separation is achieved by constructing the bounding floor, walls, and ceilings of the dwelling to comply with the required fire, sound, impact and insulation ratings.

Please note I did not use the term fire walls or separating walls. Class 2 buildings do not use fire walls or separating walls to separate dwelling units.

You can read the technical definitions of these classifications here.

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I am a Director of Development Certification Pty Ltd and have been a Building Surveyor since 1989. I have a bachelor degree in building surveying and I am a qualified carpenter. I have been in the construction industry since 1981. I have a real passion for the building certification profession as I believe building certifiers are the general practitioners of the construction industry. Our role is not only to know building law and apply it, our role includes assisting in the development of the knowledge of all in the industry by sharing our knowledge and experience.