Almost every conversation we have with a new buyer starts the same way: “Can I just put it on the back of my block? Do I need council approval?” The honest answer is “it depends” — and what it depends on is whether the building you’re buying is classified as Class 1a or Class 10a under the National Construction Code (NCC).

The short version

  • Class 1a is a permanent residential dwelling. Anyone can live in it long-term — by themselves, with family, or as a tenant. It must satisfy the full residential provisions of the NCC: structural, fire, thermal performance, energy efficiency, accessibility, and so on.
  • Class 10a is a “non-habitable” building — a shed, garage, carport, outbuilding. People can use it during the day. Nobody can sleep in it as their primary residence.

The difference matters because Class 1a is the more rigorous classification, and the only one that lets you legally let someone live in the building.

What that means in practice

If you want to put a structure in your back yard for an adult child, a renter, an Airbnb, or an elderly parent, the building must be Class 1a. Anything less and the council can issue a stop-use notice — and in most states, occupying a Class 10a structure as a dwelling voids your home insurance entirely.

If you want a workshop, a studio you visit during the day, a guest room used a handful of nights per year, or storage — Class 10a is fine, simpler, and typically cheaper.

What changes between the two

  • Engineering certification. Class 1a buildings are signed off by a Registered Professional Engineer (Queensland) or equivalent in your state, on a Form 15 (or your state’s equivalent). Class 10a usually doesn’t require an engineer’s certificate.
  • Council DA / building approval. A Class 1a build almost always requires a development application or building approval depending on your local government area. Class 10a is often exempt below a certain footprint.
  • Energy compliance. Class 1a builds in most states need a NatHERS thermal rating (currently a minimum 7-star equivalent in the 2022 NCC). Class 10a is exempt.
  • Smoke alarms, plumbing, ventilation, accessibility. Class 1a triggers full residential standards. Class 10a is sparse on these.
  • Certificate of Classification. A Class 1a build only becomes legally occupiable once the building certifier issues this. There is no equivalent for Class 10a.

How to choose

Three questions to ask yourself, in order:

  1. Will anyone sleep there as their main residence? If yes, you need Class 1a. Stop reading.
  2. Will you ever rent it out (long-term or short-term) to anyone other than family or guests for the odd night? If yes, Class 1a — your state’s residential tenancy laws and short-stay regulations require the dwelling itself to be legal.
  3. Is it ever likely to be sold as “a second dwelling on the block” rather than “a shed”? If yes, Class 1a — a buyer’s solicitor will look for the Certificate of Classification at settlement.

If you answered no to all three, Class 10a is genuinely a fine choice — and a lot cheaper to engineer and approve.

Our range

Our Class 1a range starts at the 30ft KM-Class 1a (one-bedroom, 56 m²) and runs up to the 40+40ft KM-Class 1a Multi (up to five-bedroom, 148 m²). Every one of these ships with a Form 15 (or state equivalent) and meets the 2022 NCC residential provisions.

For the “workshop / studio / store” use case, the site offices and shedsrange covers Class 10a use without forcing you to pay for residential-grade engineering you won’t use.

The one thing we will not do

Quote you a Class 10a building and let you put your tenant in it. We’ve been asked. The answer is no — it sets you up for an insurance claim refusal, a council notice, or both, and the savings on the build are not worth those outcomes.

Still unsure?

Tell us what you’re trying to put on your block. A free quote will start with whether Class 1a or Class 10a actually fits, before any prices get put in front of you.