Can you build a granny flat on your block? The NSW checklist

Most Sydney blocks that are at least 450 m², in a residential zone, with 12 m of frontage and enough room to keep the required setbacks will qualify for a granny flat through the fast approval pathway. The things that most often disqualify a block are size, frontage, heritage listing, flooding and bush fire.

Here is how to check yours, in order, starting with the questions that rule blocks out fastest.

You need at least 450 m² for complying development.

Check the figure on your title or survey, not a real estate listing.

Two traps here:

• Battle-axe blocks. The access handle is excluded from the calculation. A 500 m² title with a long driveway strip can land under 450 m² once that strip comes out.
• Rounded numbers. A block described as “about 450” is not a block that is at least 450 m². The threshold is not negotiable.

If you are under 450 m², complying development is off the table. A development application to council is still possible, and is assessed on merit.

Granny flats are permitted with consent in residential zones R1, R2, R3, R4 and R5.

For the fast complying development pathway, R5 Large Lot Residential is excluded. If you are on an R5 block, a granny flat is still allowed, but through a development application.

Your zoning is on the NSW Planning Portal, or on your council’s mapping tool.

Measured at the building line, and it steps up with lot size.

Older subdivided blocks in the inner and middle suburbs are the ones that most often fail here. A deep, narrow block can easily be over 450 m² and still be under 12 m wide.

This is the step people skip, and it is the one that decides whether the building actually fits.

Work out your required setbacks for your lot size band, then draw what is left.

Then subtract:

• Your existing house and any structures staying
• Required landscaped area, which is 20% to 45% depending on lot size, with at least half behind the building line
• Driveway and access to the granny flat
• Any tree with a protection zone
• Sewer or stormwater lines you cannot build over

What is left is your building envelope. If a 60 m² rectangle does not fit inside it with room for eaves, the answer is a smaller granny flat or a different position, not a bigger one.

Anything over 3.8 m tall increases the setbacks, so a taller design shrinks the envelope further.

Any one of these moves you off the fast pathway.

None of these are automatic no answers. They are all reasons to take the DA path or to move the building.

These do not affect whether you are allowed to build. They affect what it costs.

• Slope, which brings cut and fill and retaining
• Rock, the most common budget blowout
• Soil classification, which sets how heavy the slab needs to be
• Access for a truck and excavator
• Distance to the sewer and stormwater connection points
• Trees requiring removal or protection

All 6 yes, and you are almost certainly on the complying development pathway. Any no, and you are looking at a development application or a redesign.

You have more options than people assume.

• A development application. Council assesses on merit and can approve things the fixed checklist cannot.
• A smaller granny flat. If the envelope is tight, a 45 m² 2-bedroom often fits where a 60 m² will not.
• Repositioning. Moving the building, or removing a structure that is in the way.
• An internal conversion. A secondary dwelling inside the existing house has a different and simpler set of requirements, with no external alterations beyond one added entrance.