Granny Flat vs Duplex — Which Development?

Granny Flat vs Duplex — Which Development?

Granny flat: $150,000–$210,000, keeps existing house, 4–6 month timeline, 60 sqm secondary dwelling. Duplex: $750,000–$980,000, demolishes existing house, 14–20 month timeline, two full-size homes.

The granny flat is accessible (lower cost, simpler), while the duplex creates more absolute value and two sellable assets.

Investment Returns

Granny flat: additional rent $380–$480/week, yield on build cost 11–14%, cannot be sold separately. Duplex: combined rent $1,060–$1,300/week, yield on build cost 6.5–8%, can be sold separately (Torrens title), creates $1.8–$2.1M in property value.

Decision

Granny flat: budget under $250,000, block does not qualify for duplex, want to keep existing house, want fast/low-risk project. Duplex: budget $750,000+, block qualifies, want maximum value creation, prepared for longer project.

Some blocks support both sequentially — granny flat now, duplex later. Contact Buildana for a free assessment.