What a second storey involves
A second storey addition puts a new level on top of the house you already have. The roof comes off, a new floor structure goes on, the walls are built up, and a new roof is fitted. A staircase has to be added, and it takes space from the floor plan below. Because the existing walls and footings carry the new load, the first question is not the design but whether the house can take it.
Why people build up
A South Australian builder's guide says that in eastern suburbs such as Burnside, Norwood and Unley, smaller blocks and character overlays often push owners towards rear extensions or second storey additions. That fits what many owners tell builders: there is no room to go out, the garden is worth keeping, and a new level adds bedrooms without using up the yard. Whether it suits your house, your street and your council is a separate matter to settle with a designer and the council.
The structural checks
One builder's guide says a second storey needs structural engineering to confirm that the existing footings and frame can carry a second level, and gives $2,000 to $10,000 for that work. It adds that removing and rebuilding the existing roof can start from about $30,000, depending on span and pitch. Ask each builder who the engineer is, what they will test, and what happens to the price if the engineer says the footings need strengthening.
Stairs, plumbing and the floor below
The same guide gives $15,000 to $30,000 for the staircase, and notes that it has to be accommodated on the floor below. Bathrooms upstairs also need plumbing run through the existing house, and that can mean opening walls and ceilings. Ask how the builder plans the stair position, where the pipes and wiring will run, and what will be disturbed in the rooms you are still living in.
Living in the house during the build
Some second storey projects can be staged so that part of the house stays livable, and some cannot. A builder's guide warns that owners should plan for somewhere to live if the house becomes unlivable during the structural stage. Ask each builder to explain the stages, how long the roof will be off, how the house will be weatherproofed and whether you should expect to move out.
Costs and approvals
Published per-square-metre figures for second storeys differ: one builder gives $3,500 to $5,500 including design, engineering and approvals, and another gives $2,900 to $4,500 for construction only. The cost guide on this site shows both with their sources. A builder's guide says extensions require approval under the Planning and Design Code, and PlanSA points owners to code.plan.sa.gov.au to see the policies for an address. Ask your council what applies and ask each builder who lodges the application.
Licence and insurance
Ask for the building work contractor licence details and check it on the SA licence register. The SA Government says building indemnity insurance is required for domestic work needing council approval and costing $20,000 or more, and that the certificate must reach you and the council before work starts.
Local guides to read next
Older inner suburbs such as Unley and Norwood, coastal Brighton and Glenelg, and hillier Burnside and Mitcham each raise their own questions about the house and the street, and our suburb guides list them.
Planning the design with a builder
A second level is easiest to price when the brief is clear. Say how many bedrooms and bathrooms you want upstairs, whether the existing rooms below will be changed, and how much of the roofline you are happy to alter. A designer or builder will usually want to see the house at the front, the back and the side, and may ask for any old plans you have. The more you can show, the fewer surprises appear in the quote.
Neighbours, light and the street
A taller house affects the people next door and the look of the street. Ask each builder how the design deals with overlooking, shading and the height of the new work, and ask your council whether neighbour notification applies. A builder's guide says projects that vary from standard criteria go through a merit assessment that may include neighbour notification, and it allows four to eight weeks for that path. Ask your council and builder for a timeline of their own, in writing.
Variations and provisional sums
On a second storey, the biggest cost swings come after the roof is off. Ask each builder how they would price rotten framing, termite damage, old wiring or a floor that is not level. Ask which items in the quote are fixed and which are allowances that can change, and ask how a variation is agreed in writing before the work happens.
How much does a second storey extension cost in Adelaide?
Published 2026 guides give $3,500 to $5,500 per square metre including design, engineering and approvals, and $2,900 to $4,500 for construction only. Staircases and engineering are extra in some quotes. These are not quotes, so ask each builder what is included.
Can my house take a second storey?
Only an engineer can say. A builder's guide says the existing footings and frame must be checked and gives $2,000 to $10,000 for that work. Ask each builder how the check is done.
Will I have to move out during the build?
It depends on the house and the builder's staging. A builder's guide says to plan for somewhere to live if the house becomes unlivable during the structural stage. Ask each builder for their plan.
Do second storey extensions need approval?
A builder's guide says extensions need approval under the Planning and Design Code. Check your address on code.plan.sa.gov.au and ask your council.