Housing Code clause 3.9: maximum gross floor area for your lot in NSW

Clause 3.9 of the Housing Code (Part 3 of State Environmental Planning Policy (Exempt and Complying Development Codes) 2008) sets the maximum gross floor area of all buildings on a lot when a house is approved as complying development in NSW. The limit depends only on lot area. It is 78% of the lot for lots of 200 to 250 square metres, 75% for lots over 250 to 300 square metres, and then alternates between fixed amounts (235, 290, 335 and 380 square metres) and a formula of 25% of lot area plus 150 square metres, up to a cap of 400 square metres for lots over 1,000 square metres. For a battle-axe lot, the access laneway is left out of the lot area. The figure covers every building on the lot, including garages (apart from the excluded car space) and detached studios, so it is the first number to check before designing a new house or an extension under a complying development certificate (CDC).

Who this is for: home owners, builders and buyers planning a new house, knock-down rebuild or extension under the NSW Housing Code, who want to know the maximum floor area their lot allows and how to calculate it correctly.

What does clause 3.9 of the Housing Code say?

Clause 3.9(1) sets out the maximum gross floor area of all buildings on a lot in a table by lot area. Reproduced below:

Clause 3.9(2) adds that when calculating the lot size of a battle-axe lot, the area of the access laneway is excluded. The note to the clause confirms that “battle-axe lot” and “gross floor area” are defined in clause 1.5.

Table sourced from the New South Wales Legislation website at 29 October 2026. For the latest information on New South Wales Government legislation please go to https://www.legislation.nsw.gov.au. Legislation content is licensed under Creative Commons Attribution 4.0.

How do you calculate it? Worked examples

Two things stand out. First, the bands are not smooth: a 557 square metre lot and a 600 square metre lot sit in different bands, so the exact area on the deposited plan matters. Second, the fixed amounts create plateaus. A 610 square metre lot and a 740 square metre lot have the same 335 square metre limit. Use the figure from the survey or the deposited plan, not the agent’s rounded number.

What counts towards gross floor area?

Gross floor area under the Codes SEPP is defined in clause 1.5. The diagram under clause 3.9 illustrates how it is applied to a typical lot:

• the dwelling house is included;
• a detached studio is included;
• in an attached or detached garage, one car parking space is excluded, and the remainder of the garage is included.

Because the limit is for “all buildings on a lot”, a new house plus an existing studio, or an extension plus an existing double garage, must fit within the one figure together. Check the clause 1.5 definition for the detail of what is measured (for example, how walls, voids and stairs are treated) before finalising a design. The common mistake is calculating floor area the way a builder quotes it, including the alfresco and porch, or the way a real estate brochure does, rather than the way the code defines it.

Is the clause 3.9 figure all you can build?

No. It is a ceiling. The Department’s Guide to Complying Development (August 2023) lists the other Housing Code standards that often bite first:

• Landscaped area (clause 3.13): from 10% of the lot on lots up to 300 square metres to 45% on lots over 1,500 square metres.
• Setbacks (clause 3.10): front setbacks from 3 metres to 10 metres (or the average of neighbours), side setbacks based on lot width and building height, and rear setbacks that increase above 4.5 metres of height.
• Height and storeys (clauses 3.1 and 3.8): 8.5 metres and 2 storeys.
• Private open space and parking (clauses 3.13 and 3.16).

On narrow and small lots, setbacks and landscaped area often mean the maximum floor area can only be reached with a second storey.

Check your lot in under two minutes

1. Find the lot area on the deposited plan, survey or contract (and the access handle area if it is a battle-axe lot).
2. Open our free How much can I build? CDC calculator and enter the frontage, depth and area.
3. Note the maximum gross floor area, landscaped area and setbacks it shows.
4. Check your section 10.7 planning certificate to confirm complying development is not excluded on the land.
5. Have a planner or certifier confirm the figures against the current code before design.

Definitions

Gross floor area

The floor area measured as defined in clause 1.5 of the Codes SEPP; for the Housing Code, the total for all buildings on the lot is limited by clause 3.9.

Housing Code

Part 3 of the Codes SEPP, which allows new houses and alterations and additions in zones R1, R2, R3, R4 and RU5 to be approved as complying development.

Battle-axe lot

A lot with access to the road through a narrow access laneway (the “handle”), defined in clause 1.5; the handle is excluded from lot area for clause 3.9.

Complying development certificate (CDC)

A combined planning and construction approval issued by a council or registered certifier for development that meets every applicable code standard.

Our free CDC calculator applies the clause 3.9 table to your lot, and where the numbers are close or the lot has constraints, our DA or CDC pathway advice confirms what is achievable before you commit to a design. For a site-specific review, request a fee proposal.

Copyright note: The clause 3.9 table is reproduced from the NSW Legislation website under Creative Commons Attribution 4.0. The Guide to Complying Development is © State of New South Wales through the Department of Planning and Environment 2022; it is cited and linked, and its figures are summarised rather than reproduced.