Renovation vs Knockdown Rebuild: Cost-Benefit for 1970s Sydney Homes

Most Western Sydney suburbs have a generation of 1970s and 1980s brick veneer homes that are now hitting the renovate-or-rebuild decision. We get asked this weekly. The honest answer is: it depends on a small number of structural and lifestyle factors. Here is how to think about it.

What you typically inherit with a 1970s home

• Single brick or brick veneer construction
• Concrete slab without edge insulation
• R1.5 or no ceiling insulation
• Single glazed aluminium or timber windows
• Asbestos in eaves, electrical lining, occasionally vinyl floors
• Galvanised steel or copper plumbing (some lead pipes in earlier homes)
• Aluminium electrical wiring or early copper, often undersized for modern loads
• Floor plan with separate kitchen, dining and living rooms
• 2400mm or 2440mm ceilings, often less in passages
• Original tiled roof, often in need of repointing

Cost of a substantial renovation

For a typical 1970s 3 to 4 bedroom Western Sydney home where you want to: open up the kitchen-living-dining, replace kitchen and bathrooms, upgrade flooring throughout, replace windows, repaint inside and out, upgrade electricals and switchboard, replace roof or repoint, add insulation, extend at the rear by 30 to 50 sqm:

• Demolition and structural changes: $40,000 to $80,000
• New kitchen and bathrooms: $50,000 to $110,000
• Flooring (engineered timber or tile throughout): $25,000 to $45,000
• Windows (double glazed throughout): $35,000 to $65,000
• Roof works: $20,000 to $40,000
• Insulation upgrade: $5,000 to $12,000
• Electricals (full rewire, new switchboard, new GPOs): $25,000 to $45,000
• Plumbing upgrade: $15,000 to $35,000
• Paint and finishes: $20,000 to $40,000
• Extension at rear (45 sqm): $130,000 to $200,000
• Contingency (always 10 to 15 percent): $40,000 to $80,000

Total: $405,000 to $752,000.

Cost of a knockdown rebuild on the same block

• Demolition: $20,000 to $35,000
• Approvals: $15,000 to $30,000
• New 4 bedroom double storey Elite-tier build: $580,000 to $760,000
• Site costs (rental, storage, etc): $25,000 to $50,000
• Contingency: $35,000 to $70,000

Total: $675,000 to $945,000.

The crossover point

For a 1970s home where the renovation scope creeps to $500,000+, KDR almost always wins on value because:

• You get a brand new 30-year structure, not a patched 50-year one
• You can design to current orientation and lifestyle
• You meet current BASIX (lower energy bills for the next 50 years)
• Resale value is meaningfully higher per dollar invested
• No surprise discoveries mid-renovation (every 1970s home has them)

Below $400,000 of renovation scope, renovating is usually the right call. Between $400,000 and $500,000, it depends on the specific home and your priorities.

The lifestyle factor

Beyond money: a renovation lets you live in the home during much of the work (with disruption). A KDR requires you to move out for 9 to 14 months. Some clients have stronger reasons to stay (school zones, elderly parents, special-needs children) that tip the math toward renovation even when KDR would be cheaper per dollar.

Things that change the math

• Existing structural issues: If the existing slab has settled, has heave damage, or the frame has rot, renovation becomes much more expensive than expected. KDR removes these issues.
• Asbestos in fabric (not just eaves): If asbestos is in walls, ceilings or floors, renovation requires careful abatement. Cost can balloon. KDR demolition handles it as part of the demolition contract.
• Council tree retention: Some blocks have mature trees that limit KDR footprint. Renovation can work around them.
• Heritage controls: Heritage-listed homes cannot be demolished without specific approval. Renovation is the only path.
• Block size relative to current footprint: If the existing house already uses 70 percent of the allowable footprint, renovation has limited expansion room. KDR can replan to use the full footprint better.

Energy efficiency: an underappreciated factor

A 1970s renovation typically reaches NATHERS 3 to 5 stars. A KDR reaches NATHERS 7+ stars. Over 30 years, the energy cost difference for the household is $80,000 to $140,000 in 2024 dollars, depending on climate and usage. This is rarely factored into the renovate-vs-rebuild decision but should be.

Our honest recommendation

• If your renovation scope is under $300,000, renovate.
• If your scope is $300,000 to $450,000, run both options. The right answer depends on the specific home.
• If your scope is over $450,000, knock down and rebuild.
• If the home has heritage character or council listing, renovate (carefully).
• If you can’t move out for 9 to 14 months, renovate.