1. Detached granny flat / dependent-persons unit — Own front door, own kitchen, own bathroom. 55 – 75 sqm. Best long-term independence.
2. Attached secondary suite — Bedroom + bathroom + kitchenette + separate entry, but under the main roof. Great for parents who want proximity, not isolation.
3. Retrofit an existing room + ensuite — Fastest and cheapest. Best if the parent is highly independent today.
4. Full home reconfigure — Move the master upstairs, put a parent suite on the ground floor. Structural but future-proof.

Skip the “universal design” brochures. The features Adelaide families come back and thank us for are:

• Zero-step entry from the driveway and garage.
• Doorways 900mm+ wide throughout the parent’s zone.
• Grabrail-ready walls in the bathroom (blocking installed at framing).
• Level-entry shower with a wide fold-down seat.
• Non-slip tiles or vinyl flooring, matte finish.
• Lever-style door handles and tapware (not knobs).
• Rocker-style light switches at 900mm height.
• Motion-sensor night lights along the bedroom-to-bathroom path.
• Video intercom or smart doorbell so they never wonder who is at the door.
• A window in every habitable room — dignity, not just daylight.

The honest rule: build before you need it. Once a parent has a fall, a diagnosis or a sudden care need, timelines collapse:

• Retrofit an existing bedroom + ensuite: 6 – 12 weeks.
• Attached secondary suite: 6 – 10 months.
• Detached granny flat: 5 – 9 months once approvals land.
• Full ground-floor reconfigure: 8 – 14 months.

If a parent is 75+, the window between “fully independent” and “needs help” is often shorter than families expect. Start planning before it feels urgent.

Retrofit bedroom + ensuite for an aging parent: $65,000 – $140,000.

Attached secondary suite (bedroom + bathroom + kitchenette + separate entry): $180,000 – $320,000.

Detached granny flat (55 – 75 sqm, self-contained): $220,000 – $360,000 turnkey.

Full ground-floor accessibility reconfigure: $180,000 – $380,000 depending on structural changes.

• Most Adelaide councils allow a granny flat as a “dependent-persons unit” if it is occupied by a relative — but it must not be separately leased.
• Some councils re-rate the property once the second dwelling is added — check before you build.
• If the parent contributes to the build cost, get a written agreement in place before construction starts. Talk to a family lawyer, not just a conveyancer.
• Land tax exemptions and Centrelink assessments can change if a second dwelling is added — check with your accountant.