Why kitchen and living space leads the list
The room people most want to enlarge is usually the one they use all day. A kitchen and living extension replaces a small kitchen, a dark dining room or a narrow family room with a single open space. It is also one of the more complicated extensions, because it adds the plumbing, gas, wiring and ventilation of a kitchen to the structural work of a new room.
Open-plan means structure
Opening up the back of an older house usually means taking out walls. One builder's guide gives $8,000 to $25,000 for removing a load-bearing wall once the beam, propping and engineering are counted, and says an open-plan living extension of about 60 square metres is $150,000 to $225,000 plus a structural allowance. Those are indicative published figures. Ask each builder to identify which walls are load-bearing, who the engineer is and what is in the allowance.
Services in the new kitchen
Kitchens depend on local trades. In South Australia the licence register covers builders, plumbers, gas fitters and electricians, among others. Ask who will do the plumbing, gas and electrical work, ask for their licence numbers and check them on the register. If the old kitchen sits against an outside wall you want to move, ask what that does to the drains and the cost.
Layout, light and heat
A builder's guide says Adelaide summers regularly exceed 40 degrees and recommends deep eaves on the north and west, windows for cross-ventilation and suitable glazing. A big glass wall to the garden looks good in a photograph, but ask what it does to summer heat and how it will be shaded. Think about where the dining table, the island and the traffic through the room will sit, and where the sun will hit at lunchtime.
Fixing the scope
Kitchens are easy to blow out. Ask whether the quote includes cabinetry, benchtops, appliances, tiling, lighting and painting, or only the building shell. Ask for allowances to be written down, such as a figure for tapware or flooring, and ask what happens if you choose something dearer. Compare quotes item by item.
Approvals and insurance
A builder's guide says extensions need approval under the Planning and Design Code, and PlanSA points owners to code.plan.sa.gov.au for the policies at an address. The SA Government says building indemnity insurance is required for domestic work that needs council approval and costs $20,000 or more. Ask who lodges the application and whether the insurance is in the quote.
Older houses
If the house is old, ask each builder about asbestos before they quote. The SA Government publishes guidance for homeowners, and a builder's guide lists asbestos removal among the things that can add to extension costs. Do not disturb suspected material yourself.
Planning the layout
Before you ask for quotes, decide what the room has to do. Do you want a big island, a dining table, a lounge area, a study corner or a door to a deck? Decide where the fridge, the sink and the cooktop might go, and where people will walk. Builders and designers can improve on your layout, but they quote better when they know what you care about.
Ventilation, lighting and power
A new kitchen needs a range hood or another way to deal with cooking fumes, enough power points, and lighting you can switch in zones. Ask each builder what is included and who is responsible for the electrical design. If you are adding gas, ask about the local gas fitter and the position of the bottles or the meter. Ask what happens if the existing switchboard needs upgrading.
Floors, levels and the join
The new floor should line up with the old one, or the change should be intentional and safe. Ask how the builder would handle different levels, how the new roof will meet the old one, and how wall and ceiling finishes will match. Ask to see photographs of previous work if the builder offers them, and treat them as a starting point for questions, not as proof of quality.
Appliances and fixtures
Ask whether the quote includes the oven, cooktop, dishwasher, fridge space and range hood, or only the connections for them. A builder who allows a sum for appliances should say what it is. If you plan to reuse an existing kitchen, ask whether it can be moved without damage and what it will cost to refit.
How much does a kitchen and living extension cost?
One builder's guide gives about $150,000 to $225,000 plus a structural allowance for an open-plan living extension of about 60 square metres. Fit-out varies a lot. These are not quotes.
Can I remove a wall between the kitchen and the lounge?
Possibly, but only if it is safe. Ask each builder whether the wall is load-bearing and who the engineer is. One guide gives $8,000 to $25,000 for removing a load-bearing wall.
Do I need local trades for the kitchen?
Plumbing, gas and electrical work generally need local trades in South Australia. Ask who will do it and check the licence numbers on the register.
Can I keep cooking during the build?
Sometimes, but it depends on the staging. Ask each builder for a plan before you sign.
Sources
- RAW Structures: how much does a home extension cost in Adelaide (25 August 2026)
- Templeton Built: extension costs Adelaide (20 March 2026)
- PlanSA: find out if you need approval
- SA.GOV.AU: building work contractor's licence
- SA.GOV.AU: check occupational licence holders
- SA.GOV.AU: building indemnity insurance