KDR vs Renovation vs Extension vs Granny Flat: Which Is Right for You?

You own an older home. Something needs to change. But which path makes the most sense — financially, practically, and for your life? Here's an honest comparison of all four options.

A Quick Decision Map

Before comparing costs, ask yourself these three questions:

1. Is the structure fundamentally sound? If the frame, foundations, and roof are solid, renovation is genuinely on the table. If not, you're looking at KDR.
2. Do you need more space, or just better space? Extension adds area. Renovation improves what exists. KDR rebuilds everything. Granny flat adds a separate dwelling.
3. Are you primarily solving a lifestyle problem or an investment problem? The answer changes the maths completely.

Option 1: Knockdown Rebuild (KDR)

Best for: Old homes with structural problems, asbestos, poor layout that renovation can't fix, or homeowners who want a fully custom new home without moving suburb.

Cost range: $350,000–$700,000+ (build only, excluding land)

Timeline: 18–30 months from planning to move-in

Value created: Typically the highest uplift — new home adds 40–80% to land value in most suburbs

Key risks: Longest disruption (you must vacate), requires DA or CDC, construction cost overruns

Right move if: Your home is pre-1990s with structural issues, asbestos, or a layout no renovation can fix. Also right if you want to maximise the block's potential with a fully custom design.

Option 2: Major Renovation

Best for: Homes with good bones that just need updating — kitchens, bathrooms, open-plan living, a second storey addition.

Cost range: $80,000–$400,000 depending on scope

Timeline: 6–18 months

Value created: Moderate — a $200K renovation rarely adds $200K in value. Rule of thumb: expect 60–80 cents return per dollar spent on renovations.

Key risks: Hidden costs (asbestos, old wiring, wet rot) discovered mid-project; budget blow-outs are extremely common

Right move if: Your home has a layout you love, the structure is sound, and you're primarily improving liveability rather than maximising value. Or if you're on a tight timeline and can't wait for a full rebuild.

Option 3: Extension / Addition

Best for: Homes that need more space — an extra bedroom, a larger living area, or a second storey.

Cost range: $80,000–$250,000 for ground floor extension; $150,000–$400,000 for a second storey

Timeline: 3–12 months (DA/CDC approval time varies)

Value created: Good, especially second storey additions in land-constrained inner suburbs. A well-executed extension in Sydney or Melbourne can return $1.20–$1.50 for every dollar spent.

Key risks: Matching new work to existing structure and finishes; council setback and height limits may restrict what's possible

Right move if: You love your location and current home but genuinely need more space. Second storey additions in particular offer excellent ROI in established suburbs.

Option 4: Granny Flat / Secondary Dwelling

Best for: Homeowners with a large enough block (typically 450m²+ in NSW) who want rental income, a space for family, or to add investment value.

Cost range: $80,000–$200,000

Timeline: 3–12 months (CDC pathway in NSW is as fast as 20 days)

Value created: Properties with granny flats achieve ~27% higher rental yields. Rental income of $300–$600/week is realistic in most metro suburbs.

Key risks: Cannot be sold separately; not available on all lot sizes; ongoing landlord responsibilities if renting

Right move if: Your lot is large enough, you want income or family accommodation, and you don't need to touch the main house.

The Honest Financial Summary

The best choice depends entirely on your specific block, home condition, and goals. Run a free feasibility check on your block to get an AI assessment of which options are available to you.