These are the questions we are actually asked, on the phone and by email, week after week.
Each one is answered in a sentence first and qualified afterwards, because most of them genuinely do depend on something and an answer that hides the condition is worse than no answer. Where we have written about a subject properly, the answer says so and links to it.
Nothing here is advice about a particular property. Approval requirements vary between council areas and change over time, and the only reliable answer for your block is the one that comes with the block in front of us.
Do I need an engineer at all
Do I need a structural engineer for a home renovation in Adelaide?
You need one whenever the work changes how the house carries load, and that is a wider set of jobs than most people expect.
Removing or opening up a wall, adding a second storey, cutting into a roof, underpinning, or building anything that bears on an existing footing all change the load path and need a design. Cosmetic work does not. If you are not sure which one yours is, the cheapest way to find out is to ask before the wall is opened rather than after.
Do I need a structural engineer to remove a load-bearing wall?
Yes, any wall carrying load above it needs a designed beam, designed supports and a checked path for that load all the way down to the footing.
The beam is usually the easy part. The harder questions are what the beam bears onto, whether the footing under that point can take the concentrated load, and what replaces the bracing the wall was providing. Propping during the work should be designed too, because that is when the structure is at its most vulnerable.
Do I need an engineer for a shed, carport or verandah?
Usually yes, unless the supplier's kit comes with certification that covers your site and your footings.
Kit documentation is prepared for assumed conditions. It has to match your wind classification, your soil, and how the structure is fixed down, and it often does not cover a structure attached to the house or founded on fill. An engineer's job here is mostly footings, tie-down and the connection back to the existing building.
Can I just use my builder's engineer?
You can, and it is common, but be clear about who the engineer is engaged by and who they are reporting to.
An engineer engaged by the builder owes their duty to the builder. That is fine for most projects. If you want independent advice about work that has already been done, or a second opinion on something you have been told, engage the engineer yourself.
Approvals in South Australia
Do I need council approval for a retaining wall in South Australia?
Generally yes once the wall retains more than one metre of difference in ground level, and separately once a wall and the fence on top of it exceed 2.1 metres in combined height on a boundary.
Retaining walls are assessed under the Planning, Development and Infrastructure Act 2016 and the Planning and Design Code. Tiered walls are measured together rather than separately, and a wall carrying a driveway, a shed or a pool above it is treated differently from a garden wall of the same height. The Code is applied by zone, so check the property on the SA Planning Portal at plan.sa.gov.au or with your council before you order materials.
What is the 2.1 metre rule for fences and retaining walls in SA?
Where a fence sits on top of a retaining wall on a boundary, it is the combined height that counts, and development approval is generally required once that combined height exceeds 2.1 metres measured from the lower side.
This catches people because neither half looks like it should trigger anything. A 600mm sleeper wall is under the retaining threshold on its own and a 1.8 metre fence is an ordinary boundary fence on its own, but together they are 2.4 metres and over the line. The wall then has to be designed for the wind load coming off the fence as well as the soil behind it.
What is the difference between a structural engineer and a building certifier?
An engineer designs the structure and takes responsibility for the design. A certifier, or private building surveyor, assesses whether the proposal complies with the Building Code and grants building consent.
They are separate roles and you generally need both. The engineer's documentation is part of what the certifier assesses, which is why a design has to be prepared to be lodged rather than sketched to get a builder started.
Can an engineer certify work that has already been built?
Only where the parts that carry the load can still be inspected or verified: exposed footings, connections, member sizes and fixings.
An engineer can inspect, assess and, where the evidence supports it, provide a report on existing work. What nobody can do is certify a footing that is buried, or reinforcement that is now inside a pour, without evidence of what went in. If work is going to need certification, the time to involve an engineer is before it is covered up.
Soil, sites and Adelaide ground
Do I need a soil test before designing footings?
Yes for anything founded in the ground, because the footing design is a response to what the soil does rather than to the size of the building alone.
A soil test gives the site classification under AS 2870, which sets how much seasonal ground movement the footing has to tolerate. Large parts of metropolitan Adelaide sit on reactive clay that swells and shrinks with moisture, and the difference between a stable site and a highly reactive one changes the footing substantially.
What does a site classification of M, H1 or H2 mean?
They are AS 2870 classes describing how much a site's surface is expected to move as the soil takes up and loses moisture, from A (stable, little movement) through to P (problem sites needing specific engineering).
M is moderately reactive, H1 and H2 are highly reactive, and E is extremely reactive. The class does not say your site is bad. It says how much movement the footing has to be designed to ride out, and it is why two identical houses on different blocks need different footings.
Why do cracks appear in Adelaide houses after a dry summer?
Because reactive clay shrinks as it dries, the ground under part of the footing drops away, and the building has to span the gap.
The pattern is seasonal and it is worse where moisture is uneven: a large tree on one side, a leaking stormwater connection, a paved area keeping one edge dry while a garden bed keeps the other wet. Most of the preventable damage traces back to moisture management rather than to the footing itself.
What is a wind classification and why does it matter?
It is the wind speed your structure has to be designed for, assessed under AS 4055 from the region, the terrain, how shielded the site is and where it sits on a slope.
It matters most for light structures: sheds, carports, verandahs and fences. The same carport on an exposed ridge and in a sheltered suburban street needs different footings and different tie-down, which is why a supplier's standard detail is not automatically right for your block.
Working with us
How much does a structural engineer cost in Adelaide?
A structural engineering fee in Adelaide depends mainly on the site and the scope. Our guides give a typical Adelaide range for each common kind of work, from footing designs and new homes to retaining walls, pools and sheds.
Where a job falls in that range depends on the site (classification, slope, access), the scope, how much documentation already exists, and how much of the structure is being changed. ANS aims for a higher standard than the average at a fee below it, fixed in writing before you commit, and any variation is agreed with you before it is carried out.
What do you need from me to quote a job?
The address, what you are building, and any documentation you already hold.
Plans, a soil report, a survey or a site plan all shorten the process. If you have none of that, the address and a description are enough to start, and we will tell you what else is needed. Sending it once through the client portal keeps it with the job rather than scattered through a thread.
How long does structural design take?
It depends on the service and on when the inputs arrive. Current turnarounds for each service are listed on our services page, and you get a date for your job when we accept it.
The honest answer is that a job with a soil report, a survey and a full set of plans moves faster than one where any of those still has to be arranged. If a job needs to be brought forward, there is a priority option that is quoted and confirmed by you before anything is booked.
Do you work outside Adelaide?
Yes, we work across metropolitan Adelaide and regional South Australia, mainly in the residential industry and also in some commercial and industrial work.
We do not take on work outside our competence, and we will say so plainly if a project needs somebody else.
What standards do you design to?
The Australian Standards that apply to the work: AS 2870 for residential footings and slabs, AS 4678 for earth-retaining structures, AS 4055 and AS/NZS 1170 for wind and structural loads, and the material standards for concrete, steel and timber.
Everything that leaves the office is prepared by an engineer and checked by a second person before it is issued, and it is issued as documentation you can lodge and a builder can work from.
This page is general information about structural engineering practice in South Australia. It is not advice for a specific site, and it does not replace confirming requirements with your local council or a registered building certifier.