A garage is a non-habitable building under the National Construction Code, so converting one into a bedroom, studio or granny flat is a change of use and not a cosmetic job. It needs an approval pathway to be confirmed, a ceiling at least 2.4 m high, enough window area for light and ventilation, and a floor, walls and services that suit living in. How much it costs depends on those items, and on whether you are making a room or a self-contained dwelling.
This post covers conversions, and then extending a garage in short. For the granny flat rules in full, see granny flat council approval in NSW. For the two approval pathways, see CDC vs DA in NSW.
Why a conversion is not a simple internal alteration
The NCC says a Class 10 building is non-habitable, and that Class 10a includes a private garage, carport, shed or the like. A bedroom or living room is a habitable room. The change from one to the other is why a garage conversion is treated differently from knocking out a wall.
The complying development code for internal alterations is in Part 4 of the State Environmental Planning Policy (Exempt and Complying Development Codes) 2008, the Housing Alterations Code. Its standards for internal alterations say the development:
- must not result in a change of classification of the building under the Act or the Building Code of Australia;
- must not result in any additional separate dwelling; and
- must not result in the creation of an additional floor within a dwelling.
(Version in force 25 July 2026, with the same standards in the 8 July 2026 version. The NSW Planning Portal's home renovation page lists the same exclusions.)
Councils say it plainly. Shoalhaven City Council states that a garage is classed as a non-habitable room, that converting it to a habitable room of any description or use requires approval, and that you will need to lodge a development application. Wollongong City Council's weekly approvals lists show garage conversions going through as development applications, including a conversion of an existing garage to a secondary dwelling at Berkeley in July 2025. That is a record of how those were approved, not a rule for your house.
So the first step is to ask your council or a certifier which pathway your garage falls under. The answer can depend on whether it is attached or detached, whether the building classification changes, and what the room will be used for. Heritage, flood and bushfire controls on the block can change it as well.
Converting a garage to a granny flat
A granny flat is a secondary dwelling under the State Environmental Planning Policy (Housing) 2021. Wollongong City Council describes one as self-contained, with a habitable room, kitchen area, bath or shower and toilet and clothes washing facilities. The rules that matter most for a conversion:
| Rule | What the policy says | What it means for a garage |
|---|---|---|
| Floor area (section 52) | The secondary dwelling is no more than 60 m2, or a greater area if another planning instrument allows it. Principal and secondary dwellings together must not exceed the maximum floor area allowed for a dwelling house on the land | Measure the garage floor area before planning, because the limit applies to the secondary dwelling's floor area |
| One secondary dwelling (section 52) | No dwellings other than the principal dwelling and the secondary dwelling can be on the land | A block that already has a granny flat cannot have a second one in the garage |
| Site area (section 53) | A minimum site area of 450 m2 is a non-discretionary standard for a detached secondary dwelling | A detached garage on a block under 450 m2 is a problem. An attached or internal conversion is a different case |
| Parking (section 53) | It is a non-discretionary standard that the number of parking spaces on the site is the same as before | A garage conversion normally removes a space, so parking is likely to be raised |
| Complying development (section 54) | Where the secondary dwelling is within the principal dwelling, it is complying development if it meets the relevant provisions of the Building Code of Australia and the Schedule 1 standards, among other conditions | A certificate is possible for some garage conversions, so check this before assuming a DA |
(Housing SEPP, version in force 7 August 2026.) The conditions in section 54 are longer than this table shows, and we have not quoted all of them. Our granny flat approval post covers the key ones.
What the building code asks of a habitable room
A garage that becomes a bedroom has to meet the Housing Provisions of the NCC 2025 for habitable rooms. A certifier confirms the edition and any NSW variation that applies.
| Item | NCC 2025 requirement | Garage issue |
|---|---|---|
| Ceiling height (Part 10.3) | Habitable room excluding a kitchen: 2.4 m. Kitchen: 2.1 m. Garage: 2.1 m | A garage ceiling lower than 2.4 m, or exposed trusses, may need rework |
| Natural light (Part 10.5) | Windows with a light-transmitting area of at least 10% of the room's floor area, or roof lights at 3%. A window facing a boundary must be at least 900 mm from it | A garage often has a roller door and no windows, so new openings are needed |
| Ventilation (Part 10.6) | Openable area of at least 5% of the floor area, opening to a suitable space | Same: the garage door opening is replaced with a wall and windows |
Shoalhaven Council also lists the 2.4 m minimum ceiling height and parking as considerations. Local requirements differ.
What drives the price
We do not publish a figure for a conversion, because the garage decides the cost. These are the items that move the price, roughly in the order they come up on a site visit:
- Approval and compliance. Plans, the consent or certificate, and a building code assessment for the change of classification. A conversion to a dwelling needs more than a conversion to a room.
- The roller door opening. Infilling with a framed wall, windows and a door suited to a living space.
- The floor. A garage slab is a working floor. Whether it can take a living-room floor build-up, and what that does to the 2.4 m ceiling, is checked on site.
- Ceiling and roof. Raising or relining the ceiling to reach 2.4 m, and insulation to suit a lived-in room.
- Windows and ventilation. Enough glazing and openable area for the room, set clear of boundaries.
- Services. Power, lighting, data, heating and cooling. For a granny flat, a kitchen, bathroom and laundry bring plumbing and drainage.
- Parking. If council asks for the space to be replaced, the carport or garage you build elsewhere is a separate cost.
A bedroom or studio without a kitchen or bathroom avoids the last two, but it is still a conversion that needs approval. What happens when a self-contained flat is built or rented without approval is covered in granny flat council approval.
Extending a garage
Making a garage bigger adds new floor area, so it is priced like an extension, by area and finish. How we price new floor area is in home extension cost per m2 in NSW and on the home extension cost page. The approval question is separate from the cost question: size limits and boundary setbacks depend on your lot, so ask your certifier before you design. Our home extensions page covers how we run those jobs.
Where we come in
We assess the garage first: measured floor area, ceiling height, slab, roller door opening and where services run. From there we set out the scope, the approval pathway and a fixed-price proposal. To start, send the address and some photos of the garage through the contact page.
Sources
- State Environmental Planning Policy (Exempt and Complying Development Codes) 2008, Part 4, clauses 4.1 and 4.2, NSW Legislation
- State Environmental Planning Policy (Housing) 2021, sections 52 to 54, NSW Legislation
- Home renovation (complying development), NSW Planning Portal
- Converting a garage to a habitable room, Shoalhaven City Council
- Granny flats, City of Wollongong
- NCC 2025 Part 10.3 room heights, Part 10.5 light and Part 10.6 ventilation, Australian Building Codes Board
Common questions
Do I need council approval to convert a garage in NSW?
Usually yes. Shoalhaven City Council states that converting a garage to a habitable room of any use requires approval and a development application. The complying development code for internal alterations cannot be used where the work changes the building's classification or creates an additional separate dwelling. Ask your council or a certifier which pathway applies to your property before you start.
Is a garage conversion complying development?
Not as an internal alteration if it changes the building classification under the Building Code of Australia or creates a separate dwelling, which are both excluded by the Codes SEPP. A granny flat can be complying development under the Housing SEPP. Where the secondary dwelling is within the principal dwelling, that requires meeting the relevant provisions of the Building Code of Australia and the policy's other conditions.
How big can a granny flat made from a garage be?
The Housing SEPP caps a secondary dwelling at 60 square metres of floor area, unless another planning instrument permits more, and the principal and secondary dwellings together must not exceed the maximum floor area allowed for a dwelling house on the land. The measured floor area of the garage is what gets tested against it.
How much does it cost to convert a garage to a granny flat?
It depends on the garage, and we do not quote a figure without seeing it. The cost comes from the items below: approval and building code compliance, the floor, walls, ceiling and openings, services, and the kitchen and bathroom that make it a self-contained dwelling. A converted garage that is not a granny flat avoids the kitchen and bathroom.
How much does it cost to extend a garage?
Extending a garage is new building area, priced by the area and the type of work. Our home extension cost page and the per square metre post set out how we price new floor area. The extension itself needs its own approval check for size and boundary setbacks.
What ceiling height does a converted garage need?
The National Construction Code requires a habitable room, excluding a kitchen, to be at least 2.4 m high. A garage only needs 2.1 m. Shoalhaven Council lists the 2.4 m minimum as an approval consideration. A garage with a low ceiling or exposed roof framing may need the ceiling or roof reworked.
Do I have to replace the parking?
Council can consider it. Shoalhaven lists providing the required parking elsewhere as one of the considerations in granting approval. The Housing SEPP's non-discretionary parking standard applies where the number of parking spaces on the site is the same as before, which a garage conversion normally changes, so expect the question to come up.
Want a hand with this at your place? Get a free quote or call 0434 037 851.