Granny Flat Design in NSW: Who Designs It, Who Approves It and Who Builds It

Granny flat design in NSW involves four separate roles, and most confusion comes from mixing them up. A designer draws it. A surveyor measures the site. A certifier or council approves it. A licensed builder constructs it. LCG Architects does the first of those and manages the approval. We do not build granny flats. This guide explains the rules, the roles, and what affects the cost of the design stage.

What counts as a granny flat in NSW

Planning law calls it a secondary dwelling: a self-contained home on the same lot as a principal dwelling, with its own kitchen, bathroom and entry. It can be detached in the backyard, attached to the house, or built within it.

Two limits define it. It must stay on the same title as the main house and cannot be subdivided off and sold. And it is capped in size. Under the State housing policy the floor area limit is generally 60 square metres, unless your council's plan allows more.

The rules your block has to meet

A secondary dwelling can be approved as complying development, the fast-track pathway, when the lot and the design meet the State standards. The main tests:

• the land is in a residential zone where secondary dwellings are permitted
• the lot is at least 450 square metres for the complying pathway
• there is one principal dwelling and there will be only one secondary dwelling
• the design meets setbacks from the side and rear boundaries
• site coverage, landscaped area and height limits are met
• the land is not excluded by heritage, high bushfire risk or similar constraints

Details are published by the NSW Department of Planning. If the lot is smaller, or the design misses a standard, a development application to council is the alternative. That takes longer and is still possible on many sites.

Who designs it

An architect, building designer or draftsperson prepares the drawings. For a granny flat the design task is to fit a liveable one or two bedroom home into a tight envelope without ruining the main house's yard, privacy or sunlight.

Small buildings are less forgiving than large ones. Sixty square metres with a poorly placed bathroom feels cramped. The same area with good orientation, a proper living space and storage feels like a home. That is the difference design makes on granny flats and secondary dwellings.

Who surveys it

A registered surveyor prepares a detail and level survey before design begins. It shows boundaries, existing buildings, levels, trees, easements and visible services. Certifiers require it, and setbacks cannot be proven without it.

People often search for a surveyor for their granny flat before they have a designer. The order does not matter much, as long as the survey exists before drawings are finalised. LCG Architects is part of the LCG group, which includes a registered surveying practice, so survey and design can be arranged together.

Who approves it

For complying development, a registered certifier or council checks the drawings against each standard and issues a complying development certificate. That certificate covers both planning and construction approval. The certifier then inspects at set stages during the build and issues the occupation certificate at the end.

For a development application, council assesses and grants consent, and a certifier then issues the construction certificate. Either way, applications go through the NSW Planning Portal. Preparing the DA and CDC documentation is part of our scope.

Who builds it

A licensed builder. In NSW, residential building work must be done by a contractor with the right licence and, above a set contract value, with home building compensation cover in place.

You have two broad options. A granny flat company designs and builds from its own range of plans for a package price. Or you engage a designer independently and have builders tender on the finished drawings.

We are the second kind. LCG Architects designs, documents and obtains approval, then hands you a set of drawings that any builder can price. We do not construct, and we cannot give you a build price. If you want one company to do everything from a standard plan, a design and build firm is the right call, and we will say so.

Package builder or independent design: the trade-off

A package is simpler and often quicker to start. The plans are proven, the price is known early, and one party is responsible.

The limits are real as well. Standard plans assume a flat, regular, unconstrained block. Sloping sites, odd shapes, trees, sewer lines and privacy problems are where a stock design stops fitting. You also cannot compare prices, because the design belongs to the builder.

Independent design costs a separate fee and takes an extra step. In return the building suits the site, and you own drawings that several builders can quote on.

What affects the cost of the design stage

Design and approval fees vary with the work involved:

1. Site difficulty: slope, access, trees and easements.
2. Whether the design is fully custom or adapted from a tested layout.
3. The approval pathway. A DA needs more reports than a CDC.
4. Consultants: survey, structural engineering, stormwater, BASIX and any bushfire report.
5. How much construction detail you want in the drawings.

Council or certifier fees and any contributions are separate again. We provide a fixed-fee proposal once we have seen the site details, so the design cost is known before you commit.

Before you call anyone

• Measure your lot area from the rates notice or contract.
• Order a Section 10.7 planning certificate from council.
• Find the sewer diagram for the property.
• Decide who the flat is for: family, rental or both.
• Work out roughly where on the block it could sit.

Next step

If you want a granny flat designed for your site and approved, with drawings you can take to any builder, send us the address and your lot size. If two saleable homes is the goal, read our dual occupancy design page first.