The four multigen layouts that actually work
- Separate granny flat / dependent-persons unit — Own kitchen, own bathroom, own front door. Best long-term privacy.
- Attached wing with a shared entry — Single roof, but a locking internal door + own bathroom + kitchenette.
- Split-level dual master — Two suites at opposite ends of the house, shared kitchen and living.
- Two-storey with self-contained ground floor — Younger generation upstairs, older generation on the ground floor with zero-step access.
The right layout depends on which generation is joining, how independent they are today, and how independent they will be in 10 years.
What every good multigen home needs
- Two full bathrooms — never share the primary bathroom across generations.
- Two living areas so a nap, TV or grandkids do not conflict.
- Zero-step access to at least one bedroom + bathroom.
- Wide doorways (900mm+) in the older generation’s wing.
- Separate laundry access, even if the laundry is shared.
- Sound insulation between the two “households”.
- A private outdoor spot for the older generation — even 12 sqm of paved courtyard.
- Kitchenette (fridge + microwave + sink) on both levels if you are stacking generations.
Real Adelaide numbers (2026)
Add a separate granny flat / dependent-persons unit: $180k – $340k for 55 – 75 sqm. Council-dependent, especially on setbacks.
Attached secondary suite (new build): Adds $220k – $380k to the base build cost of a 4 – 5 bedroom home.
Retrofit an existing home for multigen: $140k – $320k depending on bathroom + kitchenette + zero-step access work.
New multigen build (single title, two wings): $780k – $1.35M for a well-designed 300 – 380 sqm home with two full bathrooms and separate living areas.
Council rules in South Australia
Most Adelaide councils allow a second dwelling as a “dependent-persons unit” if it is occupied by a relative — but it must not be leased separately. Key considerations:
- Minimum lot size varies by zone — usually 500 – 700 sqm.
- Front-of-block secondary dwellings are almost never approved.
- Setbacks from side and rear boundaries are strict.
- Some councils treat it as a full second dwelling, which changes rates and stamp duty.
Have a builder or town planner check the exact rules on your block before you commit to a layout.
The conversations to have before you build
- Who owns the property, on paper?
- How are bills, insurance and maintenance split?
- What is the plan if the older generation needs full-time care in 5 – 10 years?
- What is the plan if the younger generation needs to sell?
- How do school pickups, grandkid drop-offs and shared meals actually get scheduled?