One of the first design decisions for any NSW granny flat project is whether to build it detached (a standalone structure) or attached to the main house. Both work, both qualify for council approval, but each has trade-offs. Here is how to decide for your block in 2026.
For most NSW owners, detached is the better choice. It gives the tenant or occupant more privacy, has a cleaner approval pathway, and protects the resale value of the main house. Attached granny flats only make sense in specific situations (very small blocks, multi-generational living, accessibility constraints).
A standalone structure on your block, usually behind or beside the main house. Independent entrance, independent services, independent outdoor space.
A second dwelling that shares a wall with the main house. May have its own entrance or share through a corridor.
A modular detached granny flat from our range typically costs about 10 to 15 percent more than an equivalently sized attached granny flat. The extra cost comes from the standalone foundation, full external cladding, own roof, and independent service connections.
However, the detached version typically generates 10 to 15 percent higher rent, so the yield is similar or better.
Detached granny flats qualify for SEPP complying development if your block meets the size and dimensional rules. CDC approval is fast (around 3 weeks) and avoids the council process.
Attached granny flats often require a DA because the addition modifies the main house. Some councils have local rules that explicitly require DA for attached secondary dwellings. This can add 8 to 16 weeks to your timeline.
Choose attached if:
Choose detached if:
A practical middle ground we design often: detached granny flat connected to the main house by a covered walkway, pergola, or covered breezeway. You get the SEPP CDC pathway and full structural separation, but daily movement between buildings is comfortable in any weather.
This works particularly well for families housing an elderly parent who values independence but wants frequent contact.
If you go attached, invest in sound-rated party walls. Standard plasterboard between dwellings is acoustically thin and you will hear each other's TV and conversation. We use double-stud construction with acoustic insulation for attached granny flats to keep sound transmission down.
When you eventually sell the main house, a detached granny flat typically adds clear, quantifiable value: another rentable unit on the title. Many buyers actively search for properties with detached secondary dwellings.
An attached granny flat adds value too, but it is harder to quantify. Some buyers see it as a positive, some as a complication.
For your specific block, we look at lot dimensions, setback rules, the use case (tenant vs family), and council rules to recommend detached or attached. We have done both hundreds of times and can give a clear recommendation in a 30-minute conversation.
Book a free consultation or visit our display centre to see both types built.
