Granny Flat Size & Setback Rules in NSW

Before you draw up plans or price anything, it helps to know what the rules actually let you build. A granny flat, or secondary dwelling in the planning language, comes with a few hard limits. Most of the questions we get from people around Wollongong come back to the same three things: how big it can be, how far it has to sit from the fence, and whether it needs full council approval. Here is what the granny flat rules in NSW actually mean, in plain English.

What are the granny flat rules in NSW?

In NSW a granny flat can be up to 60 square metres of floor area, measured to the outer face of the external walls, on a residential block that is usually at least 450 square metres. It has to keep setbacks from the boundaries, and it is approved either as complying development by a certifier or through a development application with council.

The sections below cover each of those rules in turn.

Granny flat size: the 60m² floor area rule

Under the NSW Housing SEPP, a secondary dwelling can be up to 60 square metres of floor area. That is the number most people have heard, and it is a real cap, not a guideline. The area is measured to the outer face of the external walls, at a height of 1.4 metres above each floor level, so wall thickness counts toward the 60m². Schedule 1, clause 4(3) of the Housing SEPP (version in force from 23 October 2026) defines floor area as "the sum of the areas within the outer face of the external walls of each storey of a dwelling ... measured at a height of 1.4m above each floor level". Clause 10 sets the rear setback at "3m" for a lot of at least 450m² but not more than 900m².

A few things that trip people up:

• The 60m² is measured to the outer face of the external walls, not the inside face. Eaves, awnings, lift shafts, stairways and voids above a lower storey are excluded. A patio, deck or verandah that is not enclosed by a wall higher than 1.4 metres is not an enclosed attached structure, but decks have their own size and height limits, set out below.
• It stays a secondary dwelling. It shares the lot with the main house and cannot be subdivided onto its own title in most cases.
• Bigger is sometimes possible. Both the complying development and the development application rules allow a larger flat if another planning instrument, such as your council's local environmental plan, permits a greater floor area for a secondary dwelling on your land. Check your council's LEP before assuming 60m² is the end of it.

Treat 60m² as the working ceiling and design inside it. A well laid out 60m² flat, one or two bedrooms, is plenty for a rental, a teenager, or ageing parents.

Common granny flat sizes in NSW

Almost every granny flat we build lands in one of three sizes inside the 60m² cap: a studio at around 35 to 45 square metres, a one-bedroom at around 50, or a two-bedroom taking the full 60.

• Studio, 35 to 45m². Open-plan living with a kitchenette and a bathroom. The cheapest to build and the simplest to get through approval.
• One-bedroom, around 50m². A separate bedroom and a full bathroom, which is what most tenants and family members are after. 1-bedroom granny flat floor plans goes through what fits.
• Two-bedroom, up to 60m². The most you can build as a secondary dwelling. See 2-bedroom granny flat designs for how the rooms have to give a little.

The cap isn't the only thing setting your size. Setbacks, the shape of the yard and where the sewer runs often mean the biggest flat a block will take is smaller than 60m².

Minimum lot size

The other early filter is your block. In most NSW council areas the land needs to be at least 450 square metres for a granny flat, and it has to be in a residential zone. Plenty of standard Illawarra blocks clear that easily, but battleaxe blocks, older subdivisions and some Southern Highlands lots are worth checking before you get too far.

Zoning matters as much as size. If your block sits in a zone that does not allow secondary dwellings, the 450m² does not help you. That is a quick thing to confirm with your council or a private certifier, and it is worth doing first.

Granny flat setbacks: how far from the boundaries

Granny flat setbacks are the distances the building has to keep from your boundaries, and they depend on your lot size and the pathway you use. Under complying development, the side setback is 0.9 metres on a lot of 450 to 900 square metres, and the rear setback is 3 metres. Both increase on larger lots and for buildings taller than 3.8 metres. The table below has every figure by lot size.

The front is usually governed by the existing house and the street, so a granny flat generally goes behind or beside the main dwelling rather than out front. Drainage easements, sewer lines and big trees can all eat into where the building can actually land, which is why a site check early on saves headaches later.

Do not lock these numbers in from a blog post. Setbacks are the detail council and certifiers look at hardest, so confirm the exact figures for your block before you commit to a layout.

What setbacks does a granny flat need from the side and rear boundary?

A granny flat built as complying development must be at least 0.9 metres from a side boundary and 3 metres from the rear boundary on a lot of 450 to 900 square metres. Larger lots need more. Taller buildings add to both figures. The full set of limits is in Schedule 1 of the Housing SEPP.

Complying development standards for a granny flat in NSW, by lot size (Housing SEPP Schedule 1), as at 5 November 2026:

Above 3.8 metres of building height, the side setback grows by 25 percent of the extra height. The rear setback grows by 3 times the extra height, capped at 8 metres, 12 metres and 15 metres for the three lot sizes. Where two neighbouring houses are within 40 metres on the same side of the street, the front setback is the average of their setbacks instead. The secondary dwelling itself is capped at 60 m², or more if another planning instrument allows it.

What is the minimum block size and frontage for a granny flat under complying development?

The lot must be at least 450 square metres, with at least 12 metres of frontage to the primary road at the building line. The frontage requirement rises to 15 metres for lots over 900 square metres and 18 metres for lots over 1,500 square metres. The lot can have only one principal dwelling and one secondary dwelling once the work is done, and it must have lawful access to a public road.

A block that fails a standard is not ruled out. It needs a development application instead, and council assesses it on its merits.

How much of the block can the house and granny flat cover?

On a lot of 450 to 900 square metres, the house, granny flat and other structures can cover up to 50 percent of the lot. That falls to 40 percent on lots of 900 to 1,500 square metres and 30 percent over 1,500 square metres. Driveways, paving, fences, eaves, pools and unenclosed decks and patios attached to the house or flat do not count toward site coverage.

Total floor area is a separate limit. On a 550 square metre block, the house, the flat and any attached carport, garage or deck enclosed by a wall higher than 1.4 metres together cannot exceed 330 square metres. On a 700 square metre block the figure is 380 square metres.

Can you build a granny flat on a battle-axe block?

Yes, under complying development, if the access laneway is at least 3 metres wide and the lot measures at least 12 metres by 12 metres excluding the laneway. The laneway area is also left out when the lot size is calculated, so only the main body of the block counts toward the 450 square metre minimum.

The rules for the building itself are the same as on any other lot, except that the front door and street-window requirements do not apply. For the planning and subdivision side of battle-axe blocks, see Property Thrive's guide to battle-axe blocks. Our own post on building on a battle-axe block covers what the handle does to the build.

Planning rules for dual occupancy and R2 zoning sit with Property Thrive. See their R2 zoning guide for what the 2025 changes allow.

CDC versus DA, in plain English

There are two main ways to get a granny flat approved in NSW.

• Complying development (CDC). If your block and your design tick every box in the complying development rules, a private certifier can approve it without going through full council assessment. It is the faster path, and it is why the 60m², lot size and setback rules matter so much. Miss one, and you fall out of it.
• Development application (DA). This goes to council for assessment. You use it when your block or your plans do not fit the CDC boxes, for example an odd-shaped lot, a heritage overlay, bushfire or flood constraints, or a design that pushes past the standard limits. It takes longer and neighbours can comment, but it gives you room to argue a case.

Neither one is better. It comes down to what your block allows. Part of our job is working out which path is realistic for you before any money goes into design.

What's involved in building a granny flat in NSW?

Four stages: a site check against the rules, design, approval, then the build. Most granny flats around Wollongong and the Illawarra run about six to twelve months from first sketch to handover, and how long a granny flat takes to build breaks down where those months go.

The site check comes first for a reason. Lot size, zone, setbacks, easements and the sewer decide what can go where, and every design decision after that has to live inside those limits. Do it the other way around, fall for a layout, then find the block won't take it, and you pay for drawings twice.

Approval needs a proper document set: a site plan, floor plans, engineering for the footings, and a BASIX certificate for energy and water. Whether you need council approval walks through the CDC and DA paths, and our granny flat builds page covers how we run the design, the approval and the build as one job.

The honest bit

The rules above are the general NSW framework, and they hold true across Wollongong, the Illawarra and the Southern Highlands. Your block is its own story though. Local council controls, easements, overlays and slope can all shift what is possible, so the only way to know for certain is to confirm with your council or a certifier for your specific address.

That is the part we sort out early for clients anyway. We look at the block, work out whether CDC or a DA fits, and put the real limits in front of you before you get attached to a layout that the site will not allow.