The knockdown-versus-renovate question changed in Canberra on 1 July 2026, and a lot of owners have not caught up. The Missing Middle Housing Reforms mean an RZ1 block in an established suburb can now support two-storey missing middle housing, the former minimum block size for a second dwelling is gone, unit titling is available more widely, and a 50 per cent partial waiver on the Lease Variation Charge applies to eligible development until June 2029.
That turns what used to be a two-way question into a three-way one: renovate, rebuild a single house, or redevelop the block into two or more dwellings. This guide covers how to decide.
The Lease Question Comes First
All ACT land is leasehold. Before any cost comparison, read the Crown lease.
- The purpose clause sets out what the land may be used for, including the number of dwellings permitted
- A single-dwelling rebuild on a single-dwelling lease needs no lease variation
- Anything that takes the block to two or more dwellings requires a lease variation and triggers the Lease Variation Charge
- Get an estimate of that charge early. It is frequently what decides whether the redevelopment option works, and it is estimable at concept stage. Check whether your proposal qualifies for the 50 per cent partial waiver.
The Loose-Fill Asbestos Question
In Canberra this can decide the comparison outright. Loose-fill amosite insulation was installed in more than 1,000 homes in the 1960s and 1970s. Material remained after the 1988 to 1993 removal program in wall cavities, subfloors and behind cornices, and the ACT government has acknowledged it is probably still present in the community.
- If a property is affected, renovation is generally not the answer. The material cannot be worked around, and disturbing it contaminates the house and everything in it. The eradication approach has been demolition rather than remediation.
- Commission a licensed asbestos assessor on any pre-1980 house before you plan anything. A standard building inspection does not cover it.
- The ACT Loose Fill Asbestos Coordination team holds information on affected properties
Blocks where an affected house has already been demolished under the scheme are a known category in the Canberra market, and they trade as land rather than as houses.
A related guide to consider while planning this work is The Best Canberra Suburbs to Buy and Renovate for Profit.
What the Site Allows
Before comparing cost, establish what could actually be built if you demolished.
- The zone. RZ1 now permits missing middle housing up to two storeys; RZ2 up to three. This is the biggest single change to Canberra’s development landscape in decades.
- Canopy cover requirement. Now a core development control. On a treed block it frequently determines how much of the site can be built on and paved, and it applies to a new build in full.
- Protected trees and their root zones. Registered trees and trees in the Tree Management Precinct constrain the buildable footprint. An existing house may sit where a new one could not.
- Current setbacks, site coverage and plot ratio. Many ex-government houses sit closer to boundaries and cover different proportions than the current controls would allow.
- Solar access provisions, both to your block and to the neighbours.
- Heritage, where the property or precinct is on the ACT Heritage Register.
- Bushfire on the western and southern fringes, where a new build must meet the full BAL construction requirements.
- Geotechnical conditions. Rock changes the footing cost for a rebuild considerably more than for an extension, because you are excavating the whole footprint.
The Cost Comparison
Knockdown rebuild, single dwelling
- Demolition and site clearance: $30,000 to $70,000 including asbestos removal and service disconnection
- New build, volume builder standard: $2,900 to $3,900 per square metre
- New build, custom or architect-designed: $4,200 to $7,500 per square metre
- New build, high end: $7,500 to $14,000 per square metre
- Site works, footings including rock allowance, connections, driveway, fencing, landscaping: $130,000 to $350,000
- Approvals, reports and professional fees: $45,000 to $130,000
A 220 square metre custom home in Canberra lands at roughly $1.2 million to $2 million all-in, plus land.
Renovation and extension
- Renovating existing space: $3,000 to $5,500 per square metre
- Ground-floor extension: $4,400 to $6,500 per square metre
- Second-storey addition: $6,500 to $11,000 per square metre
- Envelope upgrade to the retained house: $30,000 to $90,000
- Remediation — bonded asbestos, rewire, replumb, roof: $70,000 to $200,000
- Approvals, reports and professional fees: $30,000 to $90,000
A comparable outcome — 220 square metres of good-quality space in a renovated and extended Canberra house — commonly lands at $800,000 to $1.5 million.
Two-dwelling redevelopment
- Two dwellings of 150 square metres each at $4,500 to $6,500 per square metre: $1.35 million to $1.95 million
- Demolition, site works and shared infrastructure: $180,000 to $400,000
- Lease Variation Charge, potentially substantial, with the 50 per cent partial waiver available for eligible RZ1 missing middle development until June 2029
- Approvals, reports, professional fees, unit titling: $80,000 to $180,000
- Against which: two separately saleable dwellings rather than one
When Renovating Makes Sense
- Existing site conditions favour retention. Where the house sits within setbacks or a footprint that current controls would not allow, or where protected trees and canopy cover requirements would substantially constrain a new build.
- The bones are sound and the block faces the right way. An ex-government house with the garden to the north is exactly the project a northern extension solves.
- The budget is under $700,000. Below that, renovation delivers more usable outcome.
- Mature protected trees that a rebuild would have to design around anyway, and that give the property much of its character.
- A heritage listing or precinct that constrains demolition.
- Reasonable ceiling heights and sound face brickwork in the original — the better ex-government plans are genuinely worth keeping.
- You want to stay in the house for part of the project.
- A shorter program. Nine to seventeen months rather than eighteen to thirty.
When Rebuilding Makes Sense
- Loose-fill asbestos is present. This decides it.
- The orientation cannot be fixed. Some plans on some blocks simply cannot be reoriented without effectively rebuilding around them.
- Remediation is a large share of the budget. Bonded asbestos, rewire, replumb, roof, footing repairs and a full envelope upgrade can total $300,000 before you improve anything visible.
- You want a genuinely high-performing envelope throughout. Retrofitting an uninsulated double brick house to modern thermal performance is expensive and always compromised. A new build achieves it as a matter of course — and in the ACT that difference is disclosed at sale in the Energy Efficiency Rating.
- You want substantially more house. Once the addition exceeds the existing floor area, you are building a new house with an old one attached at a higher rate per square metre.
- The block supports two or more dwellings and the Lease Variation Charge, after any waiver, makes that work.
When Redevelopment Makes Sense
The genuinely new option since July 2026.
- An RZ1 or RZ2 block with real capacity after canopy cover, setbacks and tree protection zones are accounted for
- A Lease Variation Charge that is manageable, particularly with the 50 per cent partial waiver
- A suburb where a new dwelling’s value comfortably exceeds the cost of building it
- Where unit titling works, creating two separately saleable assets on land you already own
- Where you are prepared for a longer, more complex project with a development application, a lease variation and unit titling all in the program
This is the option most likely to be overlooked, and on a large RZ1 block in Curtin, Hughes, Ainslie or Lyneham it can be substantially the best outcome. See second dwellings in Canberra.
A Worked Comparison
A 1966 double brick ex-government house of 115 square metres on an 850 square metre RZ1 block in Hughes. Current value $1.25 million. Street ceiling for a finished four-bedroom home around $1.85 million. Clear loose-fill asbestos assessment. Two protected trees at the rear boundary. Rock at 800 millimetres across part of the site.
Option one: renovate and extend to 200 square metres
- Remediation — bonded asbestos, rewire, replumb, roof: $130,000
- Renovation of the existing 115m² at $3,800/m²: $437,000
- 85m² extension at $5,600/m², including rock allowance: $476,000
- Envelope upgrade to the retained house: $68,000
- Professional fees, reports and approvals: $62,000
- Landscaping and external works: $60,000
- Contingency at 15 per cent: $185,000
- Total: approximately $1,418,000, plus fourteen months of holding costs
Option two: demolish and rebuild 200 square metres
- Demolition, asbestos, service disconnection: $52,000
- New build at $5,200/m² custom: $1,040,000
- Site works, footings including rock, driveway, fencing: $195,000
- Professional fees, reports and approvals: $95,000
- Landscaping: $70,000
- Contingency at 12 per cent: $175,000
- Total: approximately $1,627,000, plus twenty-two months of holding and rental costs
Reading the result
Renovation is roughly $210,000 cheaper and eight months faster. Both options, added to the $1.25 million existing value, exceed the $1.85 million street ceiling — which is the more important finding, and the calculation most people never run. It says that on this block, at these prices, neither single-dwelling option is an investment.
Which is precisely why the third option deserves a look. Two dwellings on the same block, unit titled, with the Lease Variation Charge reduced by the partial waiver, changes the denominator entirely — you are no longer trying to fit a $1.4 million spend under a $1.85 million ceiling, but under the combined value of two dwellings. Whether that works depends on the site’s capacity after canopy cover and tree protection, and on the actual charge assessment. It is worth an hour with a town planner and a valuer before defaulting to a renovation.
How to Actually Decide
- Commission the loose-fill asbestos assessment first. If it comes back positive, the decision is made.
- Read the Crown lease and get a Lease Variation Charge estimate if more than one dwelling is on the table.
- Check the zone and get advice on Missing Middle capacity after canopy cover, setbacks and tree protection zones.
- Get the arborist report. It affects both options and it may rule out part of the site entirely.
- Get the geotechnical investigation. Rock affects a rebuild more than an extension because you excavate the whole footprint.
- Get a building inspection covering roof, wiring, plumbing, subfloor and structure.
- Get an existing Energy Efficiency Rating, which tells you honestly how far the retained house has to travel.
- Establish the street ceiling from actual sales in the last twelve months, and separately establish what a new dwelling in that suburb sells for.
- Price all three options properly, sketch each, and get outline figures from a quantity surveyor or an experienced builder.
- Compare all-in against all-in, and against the ceiling, including the existing property value.
Canberra is currently one of the most interesting decision environments in the country for this question, because the rules changed recently and the market has not fully repriced. Do the site investigation before you commission a design, run all three options, and the answer is usually clear.
A related guide to consider while planning this work is How Much Does a Home Renovation Cost in Canberra? A 2026 Price Guide.
For the numbers behind each path, see the Canberra renovation cost guide, home extensions in Canberra and the best Canberra suburbs to buy and renovate for profit.
The Non-Financial Factors
The arithmetic decides most comparisons, but not all of them, and it is worth being explicit about what does not appear in a spreadsheet.
Arguments for renovating that are not about money
- Mature protected trees and an established garden. In Canberra these cannot be recreated in a lifetime, they are legally protected, and they do real work shading the house in summer.
- Genuine mid-century character. The better ex-government plans and the architect-designed houses of the period are increasingly valued and cannot be reproduced convincingly.
- Sound face brickwork and hardwood floors, which most of this stock has and which are better than what would replace them.
- Staying in the house for part of the project — though not through a Canberra winter with the heating disconnected.
- A shorter, less disruptive program — nine to seventeen months rather than eighteen to thirty-one.
- Less embodied carbon and less waste, which matters to a meaningful share of the Canberra buyer pool.
Arguments for rebuilding that are not about money
- Getting the orientation right. Some houses simply face the wrong way, and in a climate where winter sun is a heating system, that is not a small thing.
- A genuinely high-performing envelope, achievable as a matter of course in a new build and always compromised in a retrofit — and disclosed at sale through the Energy Efficiency Rating.
- Certainty. A rebuild has fewer unknowns. There is no moment in month three where the wall comes off and reveals something.
- A single coherent design rather than a resolved compromise.
- Ending the asbestos question permanently.
Both lists are legitimate. The mistake is not choosing one over the other — it is making the choice on these grounds while telling yourself it was made on the numbers.
What a New Build Must Achieve That an Existing House Does Not
This asymmetry decides more Canberra comparisons than owners expect. An existing dwelling enjoys the conditions it was built under. A new one must satisfy the current Territory Plan and the current Code in full.
- Canopy cover. A specified proportion of the block must be capable of supporting tree canopy. On a block where the existing house covers a large footprint, a new dwelling may have to be smaller.
- Current setbacks, plot ratio and site coverage. Many ex-government houses sit in positions that current controls would not permit.
- Solar access provisions, to your block and to the neighbours’, which constrain two-storey forms in particular.
- Current energy performance requirements across the whole dwelling — which is an argument for rebuilding if performance is your priority, and a cost if it is not.
- A full engineered foundation system designed for the actual ground, which where rock is present is a significant cost across the whole footprint rather than just an extension.
- Tree protection zones applied to the entire new footprint, not just the part that is new.
On a treed inner-suburb block with a house sitting comfortably within its setbacks, a rebuild can genuinely deliver less usable house than the one you demolished. That is discoverable before you commit by asking a designer or town planner a single question: what could actually be built here today?