Do I need a structural engineer? Engineer, certifier or building inspector in the ACT

What does a structural engineer do?

A structural engineer works out whether a building, or part of one, will carry its loads and stay where it is. Then they design what's needed, or explain what has gone wrong and what to do about it.

For a house, that usually means one of four things:

• Inspect and diagnose: cracks, sagging floors, sticking doors, a leaning wall, or a structure built without approval.
• Design: beams where a wall comes out, footings and slabs, retaining walls, carports, decks, pools and extensions.
• Report: a written report with the findings, the likely cause and what to do next.
• Certify: an engineer's letter or certificate about one specific structure or element.

An engineer doesn't build the work, give building approval or issue the certificate of occupancy. We're engineering only: we don't sell or carry out repairs or building work, and we don't recommend contractors, so our advice isn't tied to a sale.

Engineer, certifier or building inspector: who does what in the ACT?

Each role has its own job, and most building projects use several of them. Here is who does what.

Sources: Building Act 2004 ss 26 and 69; Building (General) Regulation 2008 s 34; Civil Law (Sale of Residential Property) Act 2003 s 9; Access Canberra Construction Note 2026-04; ACT loose-fill asbestos awareness page.

The builder's role is to build. On a structural job they work from the engineer's drawings and the approved plans, so most jobs need an engineer first and a builder second.

Which jobs normally need a structural engineer?

Most jobs that need building approval need some engineering, because the certifier has to see how the structure works. For houses (class 1) and class 10 structures such as garages, carports, sheds and decks, the Registrar's form AF2025-18 sets the minimum documents a certifier lodges. They include:

• footing and slab details, with the "nominated founding depth and description of founding material", reinforcement, slab preparation and concrete strength;
• retaining wall details: drainage, founding levels and backfill;
• masonry details, framing and bracing, tie-downs and fixings.

When those details are on the engineer's plans, the certifier notes "Engineering Plans" on the checklist. These are the jobs that most often lead there:

• Removing a load-bearing wall. It's never exempt from building approval, and someone has to design the beam, posts and footings. See wall removal and beam design.
• Extensions and second storeys. New loads go onto old footings and framing. For the structural parts of an extension, you almost always need an engineer.
• Pools on slopes or close to the house. No ACT rule requires an engineer for every pool, but a shell on a slope, near house footings or near a sewer main needs design.
• Building near a sewer or stormwater main. Icon Water's guidance says its own approval is needed before building work starts, and footings near its pipes need care.
• Cracks with no clear cause. Before anyone prices a repair, the cause needs finding. See structural inspections and reports.

If my project is exempt from approval, do I still need an engineer?

Often, yes. An exemption means you don't need building approval. It doesn't mean the structure designs itself.

Take a small open building such as a deck, carport or pergola. It needs no building approval if it has no walls, is no more than 3 m high, has a roof of 25 m² or less, a floor no more than 1 m above the ground, and no unsupported span or cantilever over 4 m. A retaining wall needs no building approval up to 1.2 m, measured from the top of the wall to the lowest ground beside it.

Those structures still carry people, roofs, soil and water. Every exemption also comes with a condition: the work must not affect the structural integrity of any part of a building. A pergola bolted to the house, or a wall holding up the ground along a boundary, is where a design earns its fee.

Planning rules can be stricter than the building ones. A retaining wall within 1.5 m of a side or rear boundary is only exempt from development approval up to 0.4 m. And a new house is never exempt: the ACT says there are no building approval exemptions for detached houses. The details are in our guides to development and building approval in the ACT, carport, pergola and deck approval and retaining wall rules.

Do structural engineers need to be registered in the ACT?

Yes, since 6 March 2025. Under the Professional Engineers Act 2023, a person who develops or oversees structural engineering designs for an ACT project must be registered, including when the work is done from outside the ACT. The exceptions are work done under the direction and oversight of a registered engineer who is responsible for it, and work done only to a prescriptive standard. Registration belongs to the individual, not the firm, and anyone can look it up on the public register. Our guide to checking an engineer's registration in the ACT shows how.

Who should I call first?

Call whoever answers the first question your problem raises. This covers the common starting points.

1. A crack, a sticking door or a sloping floor

   The first question is what's causing it.

   A structural engineer first, to find the causeNot a repairer who sells the fix

2. Buying a house

   The seller's building and compliance report comes with the contract. It's a visual inspection report.

   A structural engineer if the report, or your own eyes, raise a structural concernThe report's writer for questions about the report itself

3. Renovating, extending or taking out a wall

   You need plans, a structural design and an approval, in that order.

   A designer or architect, then a structural engineer, then a licensed certifier

4. A deck, pergola or extension built without approval

   The questions are whether it's sound and what it would need.

   A structural engineer for an assessment, then your certifier

5. Bushfire, loose-fill asbestos, trees or boundaries

   These sit with other specialists, not a structural engineer.

   A bushfire consultant, a Class A licensed asbestos assessor, an arborist or a registered surveyor

When should you call a structural engineer?

Call a structural engineer when the answer depends on how a structure carries load. That means before you remove a wall, add a storey, build a retaining wall or a pool on a slope, or pay for a repair to a cracked house. Call one too when a report flags something structural and you need to know whether it matters, whether that's the seller's report, an inspector's report or a contractor's quote.

Starting prices, ex GST with the inc GST figure beside. Your fixed quote confirms the price before anything is booked.

The same prices apply in every Canberra district and in Queanbeyan, Jerrabomberra and Googong. Send a few photos or your plans through the form, up to 5 files, and we reply with a fixed quote in under 20 minutes on average, during business hours. Everything we do is on our home services page.