New house, same block
Knock-down rebuild engineering in Canberra
Demolition, old footings and new cut or fill can change the ground your new house sits on. We classify the cleared block, design the footings and slab, and give your certifier the structural details for building approval.
- Fixed quote for the new house's engineering, from your plans
- Fixed quote in under 20 minutes on average, during business hours
- Footings and site class from $1,290 + GST ($1,419 inc GST), soil test at cost
Prefer to talk? Call 02 6189 9876
Or email info@canberrastructuralengineers.com.au
Monday to Friday, 8:00am to 5:00pm
- Engineering onlyWe never sell the repair or the build.
- Fixed quote per jobPriced from your photos or plans before we start.
- Fixed quote in under 20 minutes on averageDuring business hours, Monday to Friday.
- Canberra and the Queanbeyan sideEvery district, plus Queanbeyan, Jerrabomberra and Googong.
In short
Knock-down rebuild engineering in Canberra is a fixed quote, priced from your new house plans. It usually covers a site classification of the cleared block and the footing and slab design your certifier needs, which on its own starts from $1,290 + GST ($1,419 inc GST), soil test at cost. Half of a duplex needs extra care for the home next door. Same prices across Canberra, Queanbeyan, Jerrabomberra and Googong.
- Fee
- Fixed quote, set from your new house plans
- Quote
- Fixed, in under 20 minutes on average, during business hours
- Footings and site class
- From $1,290 + GST ($1,419 inc GST), soil test at cost
- Dilapidation report
- From $750 + GST ($825 inc GST) for the home next door
- You receive
- Site class, footing and slab design and drawings for your certifier
- Area
- Every Canberra district, plus Queanbeyan, Jerrabomberra and Googong
Do I need a structural engineer for a knock-down rebuild?
Yes. The new house needs building approval with footing and slab details, and those start with a site classification of the cleared block. The rest depends on your plans.
There are no building approval exemptions for detached houses in the ACT, so your new home needs building approval (BA) from a licensed certifier. The Registrar's form AF2025-18 lists what the certifier must lodge for a house, including footing and slab details with the "nominated founding depth and description of founding material", and framing, bracing, tie-downs and fixings.
Those details are engineering. Here's what we design for a rebuild; your fixed quote lists the parts your plans need and says if a site visit is needed.
| Part | What we provide |
|---|---|
| Site classification | How much the soil moves as it wets and dries, from a soil test we arrange at cost |
| Footings and slab | Founding depth and material, reinforcement and cover, slab preparation, concrete strength |
| Frame | Bracing, tie-downs and fixings, plus steel or concrete beams |
| Retaining walls | Drainage, founding levels and backfill where the house cuts into a slope |
| Duplex party wall | The shared wall that stays, and how the new footings sit beside the old ones |
Why does a cleared block need a new site classification?
Because demolition, old footings and any cut or fill can change the ground. What was known about the ground under the old house may not describe the block you'll build on.
A site classification sorts your block by how much its soil moves as it wets and dries, from class A (little or no movement) to class P (problem sites, such as uncontrolled fill). It sets how stiff and deep the footings and slab need to be. Our footing, slab and site classification service explains each class.
Geotechnical reports published for individual new-estate blocks say the class must be reassessed after cut or fill, and that uncontrolled fill means "Class P conditions". After a demolition we look at:
- old footings, slabs or piers left in the ground
- trenches and holes backfilled with loose soil
- old pipes and drains, and where the sewer runs
- how far down firm ground is, across the whole footprint
That last point matters in Canberra. The rock here is often deeply and unevenly weathered, so it can be near the surface at one end of a block and metres down at the other.
Can I knock down one half of a duplex?
Not under the demolition exemption. Demolishing a single dwelling is DA-exempt only if there's no shared party wall and the neighbours get written information before demolition starts. Your certifier or the planning authority confirms the path for a duplex half.
Canberra built red-brick duplexes in the 1920s at Blandfordia and Reid, and again after the war. Some sit inside a registered heritage precinct, which adds its own limits.
The risk to the attached home is real. Canberra Times reporting describes a 2013 case in Yarralumla where an owner's half was left with "gaping holes in her walls" after the other half was demolished.
Two pieces of engineering help. Before work starts, a dilapidation report records the neighbouring home's condition with dated photos. Then the design for your new house deals with the shared wall: whether it stays, how it is supported during and after demolition, and how your new footings sit beside the old ones.
Which Canberra houses get knocked down, and which can't?
The answer depends on what the house is and where it stands. The engineering for the new house is much the same; what comes before it is not.
| Old house | What to know | Engineering we provide |
|---|---|---|
| 1960s ex-govvie | Canberra Times reporting on the 400 Series houses says owners commonly knock them down. Some extend instead; see renovating an ex-govvie. | Site classification, footings and slab for the new house |
| Garden City cottage in a heritage precinct | Demolishing an identified dwelling is allowed only in exceptional cases, and the application must include a professional structural assessment. | The structural assessment; see older and heritage homes |
| Half of a duplex | The single-dwelling demolition exemption doesn't apply where there's a shared party wall. | A dilapidation report next door, and the shared wall in the new design |
| Former Mr Fluffy block | Most known affected houses have now been demolished. The remediated blocks, spread across older districts such as Woden and Weston Creek, are resold and rebuilt. | The same as any cleared block: site class, then footings |
What else applies to a new house in Canberra?
New homes are all-electric and built to NCC 2022 or NCC 2025. These are the rules that touch the structure; the full approvals checklist is in our knock-down rebuild guide.
- Development approval. A new single dwelling is DA-exempt only if it meets the single dwelling development controls and the neighbours are informed. Your designer checks this against your plans.
- Building code edition. Building approvals from 1 May 2026 to 30 Apr 2027 nominate NCC 2022 or NCC 2025, each with its ACT Appendix, and can't mix them. NCC 2025 is mandatory from 1 May 2027, unless a DA or works approval application was lodged before 1 Nov 2026.
- No gas. No new gas network connections are allowed, including for redevelopments. If your plans put solar panels or plant on the roof, we allow for them.
- Protected trees. A tree management plan is compulsory in DA and BA where a protected tree may be affected, including a neighbour's tree. Footings near one are designed around its protection zone. See protected trees and building.
What sets the price of rebuild engineering?
It's a fixed quote, set from your plans before we start: the size of the house, the number of storeys, the slope, the soil, and how many drawings your certifier asks for.
Every published price is on our prices page.
What happens next?
We're engineers only. We don't demolish, build or recommend builders, so the design is about your block, not a sale.
Send your plans
Use the form above, or our full quote form. Add up to 5 photos or plans.
Get a fixed quote
In under 20 minutes on average, during business hours. It lists what we'll design and says if a site visit is needed.
Site class and design
We arrange the soil test, classify the block and send the footing, slab and structural drawings for your certifier.
Often needed on a rebuild
Every service is quoted at a fixed price before we start. Send photos or plans and we reply in under 20 minutes on average, during business hours.
Footings, slabs & site classification
Site classification and footing or slab design for new homes, rebuilds, granny flats and extensions, with the soil test at cost.
$1,290 + GST($1,419 inc GST) See the service
Dilapidation reports
A dated, photographed record of a building's condition before nearby demolition, excavation or building work starts.
$750 + GST($825 inc GST) See the service
Granny flats & dual occupancy
Slab, footing, frame and retaining engineering for a secondary residence or a second home on your block.
Fixed quotefrom your photos or plans See the serviceKnock-down rebuild questions
Something else on your mind? Call 02 6189 9876, email info@canberrastructuralengineers.com.au or send photos for a fixed quote.
How much does knock-down rebuild engineering cost in Canberra?
It's a fixed quote from your plans. The size of the house, the number of storeys, the slope and the soil set it. Footing and slab design with a site classification starts from $1,290 + GST ($1,419 inc GST), with the soil test at cost.
When should I get the engineering done?
Alongside your plans, before you apply for building approval. The certifier needs the footing and slab details to approve the new house, and the site class can change the slab design.
Will my builder's standard slab suit my block?
That depends on your block's site class. A slab designed for one class may not suit another. We can classify the site and design for it, or give a desktop review of an existing design from $390 + GST ($429 inc GST).
Do I need a dilapidation report on the house next door?
No ACT law requires one. Master Builders ACT advises treating it as essential before demolition or excavation. A dated, photographed record of the neighbouring home starts from $750 + GST ($825 inc GST).
Can you engineer a granny flat on the same block?
Yes. If your plans include a secondary residence beside the new house, we can engineer both. See granny flat and dual occupancy engineering.