A granny flat built like the house, not like a shed

There are two numbers. The build cost covers the dwelling and is fairly predictable. The site cost covers what your block demands: excavation, rock, tree removal, service connections, restricted access and stormwater. That's where the variation lives. We price both separately and itemise the site cost, so you can see whether another quote has included the same things or left them out until later.

In NSW the State Environmental Planning Policy for secondary dwellings sets minimum lot requirements, and councils apply their own controls on top. Lot size is only part of it — width, setbacks and how much private open space is left over all matter. The quickest answer comes from us looking at the block.

If the site and the design meet every criterion, a secondary dwelling can be approved as complying development, which is materially faster than a development application. Easements, flood or bushfire mapping and heritage conservation areas commonly push a job back to a DA.

A secondary dwelling approved under the NSW policy can generally be rented separately, which is one reason the pathway exists. It cannot usually be subdivided off and sold as a separate lot — that is a different process altogether.

Approval is the variable. Complying development is measured in weeks where everything lines up; a DA is measured in months. The build itself is more predictable once approval is in hand and services are sorted.

Site costs cover getting the work done on your particular block: access for materials, excavation, retaining on a slope, drainage, and running services to the rear. They vary enormously between properties, which is why an honest quote identifies them separately rather than hiding them in a headline price.

Not identically, but it should sit comfortably with it. Rooflines, eaves and external materials that relate to the main dwelling tend to read better and hold value — and in a conservation area it may be a requirement rather than a preference.

Your money is protected. A granny flat build clears the $20,000 threshold, so it carries Home Building Compensation Fund cover, and we send you the certificate before we take a deposit or start work. If we couldn't finish the build or fix a defect, you can claim up to $340,000: six years for major defects, two years for everything else.

Statutory warranties under the NSW Home Building Act apply automatically and cannot be contracted out of — six years from completion for a major defect, two years for anything else, plus an extra six months if a defect surfaces in the final six months of that period. It sits alongside the certificates and occupation certificate you get at handover.