Adding a Second Storey in Adelaide: What Your Existing Walls Need to Confirm First
The short answer
A second storey addition does not sit lightly on top of an existing Adelaide home—every wall, footing and connection underneath it now has to carry more load than the original design allowed for. Before any framing for the new level goes up, the existing structure, the site and the approvals pathway all need to be confirmed, not assumed from how the house looks from the street.
Assessing the existing structure before a second storey addition
A single-storey home is typically designed to carry its own roof and ceiling load down through its walls to footings sized for exactly that. Adding a second storey introduces new floor, wall and roof loads that the ground-floor walls, footings and foundations may never have been designed to carry.
What an engineer needs to check
A structural engineer working from the existing drawings—and, on an established home, an on-site inspection—confirms which ground-floor walls can carry the new load path, whether footings need underpinning or replacement, and how the new upper-level framing connects down through the existing structure to the ground. Wall framing, connections and the load path down to the footings sit within the structural provisions of the National Construction Code’s Housing Provisions, and the specific detailing depends on the documented design for the project rather than a general rule of thumb.
Source: ABCB, NCC 2022 Housing Provisions, Part 2.1 Scope and application of Section 2 (Structure).
Previous renovations can change the picture
Many established Adelaide homes have already been altered—an earlier extension, a removed wall or a converted garage can mean the load path is different from what the original plans show. That is one reason the engineer’s on-site inspection matters as much as the drawings when a second storey addition is being planned for an existing house rather than a new build.
Framing the new level once the design is confirmed
Once the engineer has confirmed what the existing structure can carry and designed any strengthening required, the upper level itself still needs framing decisions made against the documented structural requirements for a Class 1 building.
Timber wall framing for the addition is typically sized and braced against span tables in the timber-framing standard referenced by the NCC, while a steel-framed upper level follows the Housing Provisions’ structural steel member requirements instead. Bracing for wind and, where relevant, earthquake loads is assessed for the completed two-storey form—not the original single-storey building—so bracing that was adequate before the addition may not remain adequate afterwards.
- Engineer's design confirming which existing walls and footings carry the new load
- Whether underpinning, footing replacement or new footings are required
- The framing material and bracing design for the completed two-storey form
- How new framing connects to existing walls, floors and roof structure at each junction
- Temporary support and sequencing for the stage when the roof is open to weather
Sources: ABCB, NCC 2022 Volume Two, Part H1 Structure, ABCB, NCC 2022 Housing Provisions, Part 6.3 Structural steel members and WoodSolutions, AS 1684 code compliance.
Why Adelaide conditions matter for a second storey addition
Across the Adelaide Plains, reactive clay soils mean footing performance depends heavily on the site classification, and a footing sized for a single-storey load may need underpinning or replacement before it can safely carry an added level. Established homes in suburbs such as Norwood, Unley and Prospect sit inside a Local Heritage overlay or State Heritage Area in some streets, and additional planning consent—not only building consent—may apply where a second storey would change the street-facing form of a heritage-listed or contributory building.
Properties in the Adelaide Hills and hinterland can also sit within a designated bushfire-prone area, which affects the construction requirements for the new upper-level walls, windows and roof under the NCC once a Bushfire Attack Level assessment is obtained.
Sources: CSIRO, Foundation Maintenance and Footing Performance, Department for Environment and Water, Living in a State Heritage Area and SA.GOV.AU, Bushfire building regulations.
Approvals and licensing for the addition
A second storey addition is substantial building work, and South Australia’s planning system generally requires it to go through a development application and a building consent check against the National Construction Code before construction starts. Depending on the property, height, setbacks and any heritage or character overlay, planning consent may be required in addition to building consent—PlanSA’s online tools confirm what a specific address and scope of work needs.
Domestic building work in South Australia generally needs to be carried out by, or under the supervision of, a licensed building work contractor. Confirm licensing for whoever is responsible for the structural framing, propping and connections before the addition is scheduled.
Sources: PlanSA, Find out if you need approval, PlanSA, Building consent and SA.GOV.AU, Building work contractor’s licence.
Sensible next steps
Get the existing structure assessed
Engage a structural engineer before any design work locks in a floor plan, so the existing walls, footings and load path are confirmed—or their required strengthening is scoped—first.
Confirm the approvals pathway
Check with PlanSA or the relevant council whether planning consent applies in addition to building consent, especially where a heritage overlay, character area or bushfire-prone zoning is involved.
Lock in the framing design
Confirm the framing material, bracing design and connection details for the completed two-storey form before ordering materials or booking trades.
Sequence the build around the exposed roof stage
Agree how the site is protected and weatherproofed while the existing roof is removed and the new level is framed, and line up the licensed contractor responsible for that stage.
Who should be involved
- Structural engineer
- Assesses the existing walls and footings, designs any required strengthening and specifies the framing and bracing for the new level.
- Building designer or architect
- Develops the floor plan and elevations and coordinates planning matters such as setbacks, overlooking and heritage or character requirements.
- Licensed building work contractor
- Carries out or supervises the structural work, in line with South Australian licensing requirements.
- Building certifier or PlanSA portal
- Assesses the documented design against the National Construction Code and confirms whether planning consent is also required.
- Elite Surface Group walling team
- Installs the engineered framing for the new level, connects it cleanly to the existing structure at each junction, and coordinates with the certifier’s sign-off before linings and finishes proceed.
Common questions
- Can our existing walls definitely carry a second storey?
- Not without assessment. Only a structural engineer working from the drawings and an on-site inspection can confirm whether the existing walls and footings can carry the added load, or what strengthening they need first.
- Do we need planning consent as well as building consent?
- It depends on the property, height and any heritage, character or bushfire overlay. Use PlanSA’s approval check or ask the relevant council before design work is finalised.
- Can Elite Surface Group design the second storey addition?
- No. Structural design and planning approval sit with the engineer, designer and certifier. Once that design is approved, we install the engineered walling for the new level and coordinate with the finishing trades.
Sources and further reading
- Australian Building Codes Board
- NCC 2022 Housing Provisions, Part 2.1 Scope and application of Section 2, NCC 2022 Volume Two, Part H1 Structure and Part 6.3 Structural steel members
- WoodSolutions
- AS 1684 code compliance
- Department for Environment and Water
- Living in a State Heritage Area
