The space above a garage is not automatically ready to build on.
A garage can look like an obvious place for another room. Its position may suggest a separate retreat, home office or an extension of the main bedroom zone. But an open space above a roof does not establish that the supporting structure is suitable.
Ask an engineer and building professional to assess the garage, its relationship to the home and the proposed new level. Do not assume that existing walls, foundations or framing were designed for an occupied room above.
Solve the stairs and connection first.
Where would you enter the new space? A stair location can influence the garage, the main house and the shape of the proposed room. Review the design as a whole rather than treating the upper room as a box on a roof.
Explain how you want to use it. A quiet office, a teenager's retreat and a master suite each raise different questions about bathrooms, storage, privacy and everyday access.
Questions for the design brief.
Ask what investigation is required before design, whether the garage remains usable, how the build interfaces with the existing roof, and what work is needed downstairs. Include services, noise separation, weather protection and the appearance from the street in the discussion.
If you are considering a separate dwelling or rental use, say so explicitly. It is not the same brief as an extra room in the main home, and may involve different planning, access and servicing requirements. Get property specific advice rather than assuming separate occupancy is permitted.
Start with the intended use.
On the enquiry form, choose Addition above a garage and describe the room you want. Include whether the garage is attached, whether you have drawings and any known access constraints.
Official resource: ABCB guidance on extensions and building compliance.
Explore an above garage addition