You have a set of architectural plans and a floor space ratio control. The question is how much of the building actually counts.
In NSW, gross floor area (GFA) is the planning-defined floor area of a building, used to test it against controls such as floor space ratio (FSR). Under the Standard Instrument, GFA is measured from the internal face of external walls, at 1.4 metres above each floor, with specific inclusions and exclusions. Always check the instrument that applies to your site.
That last sentence matters. Most councils’ local environmental plans (LEPs) use the Standard Instrument definition, but some state policies, such as the Housing SEPP for seniors housing and the Codes SEPP for complying development, use their own versions.
What Is Gross Floor Area?
GFA is a planning measurement, not a construction or leasing one. It answers a single question: how much floor space does this building put on the site?
The Standard Instrument defines it as the sum of the floor area of each floor of a building, measured from the internal face of external walls (or of walls separating it from another building), at a height of 1.4 m above the floor. The definition then:
- includes mezzanines, habitable rooms in a basement or attic, and any shop, auditorium, cinema and the like in a basement or attic
- excludes common vertical circulation, certain basement areas, plant rooms, required car parking, loading spaces, low-walled terraces and balconies, and voids
Each of those is explained below.
How Is GFA Measured in NSW?
Three parts of the definition do most of the work: which floors, which wall face, and at what height.
Which floors
Every floor of the building, from basement to roof level, is a candidate. You start with all of them and then apply the inclusions and exclusions.
Is GFA measured from the inside or outside of the wall?
From the inside. Under the Standard Instrument, you measure to the internal face of the external walls or the internal face of a wall separating your building from another. Wall thickness is not counted.
Internal partitions are a different matter. You measure through them, so the floor area under internal walls, columns and partitions stays in the GFA.
In some decisions, the Land and Environment Court has treated an “external wall” as one that weatherproofs the interior. A breezeway or corridor that is genuinely open to the weather, for example behind open battens or fixed open louvres, may not be enclosed by an external wall at all.
Why is GFA measured at 1.4 metres?
The 1.4 m height sets the line where you read the wall face. It means skirtings, footings and nibs at floor level don’t decide the boundary; the wall at roughly chest height does.
This matters most where walls are not vertical. Think of an attic under a sloping roof, or a facade that leans in or out. On plan, the floor slab may look larger than the area enclosed at 1.4 m. The GFA is the area inside the wall at that height, not the slab edge or the building footprint.
It also explains how stairs are treated. At 1.4 m above a floor, a stair or lift shaft often appears as an opening rather than a standable floor, which is why some Court decisions have treated such areas as voids at alternate levels.
GFA is also not the same as net lettable area (NLA) or the area a tenant can use. It is a planning number only.
What Is Included in GFA?
As a rule of thumb, any enclosed floor inside the external walls counts unless an exclusion applies. Typical included areas are:
- living rooms, bedrooms, kitchens, bathrooms and laundries above ground
- private internal corridors and hallways
- offices, shops, retail floor space and commercial tenancies
- enclosed common areas such as lobbies and amenities (other than common vertical circulation)
- mezzanines, which the definition expressly includes
- habitable rooms in a basement or attic
- any shop, auditorium, cinema and the like in a basement or attic
- enclosed balconies or “wintergardens” with closable windows or louvres
- private stairs and lifts inside a single dwelling, subject to the void treatment explained below
- garbage and storage rooms that are not in a basement
What Is Excluded From GFA?
The Standard Instrument lists seven exclusions. Each comes with conditions, so read the wording closely:
- Common vertical circulation, such as lifts and stairs shared between multiple occupancies.
- Basement storage, and basement vehicular access, loading areas, garbage and services.
- Plant rooms, lift towers and other areas used exclusively for mechanical services or ducting.
- Car parking to meet any requirements of the consent authority, including access to that parking.
- Space used for loading or unloading goods, including access to it.
- Terraces and balconies with outer walls less than 1.4 m high.
- Voids above a floor at the level of a storey or storey above.
Two common simplifications are wrong. “All parking is excluded” ignores the requirement test in exclusion 4. “All basements are excluded” ignores that only certain basement uses are listed, and that habitable rooms and shops in a basement are expressly included.
Element-by-Element GFA Guide
Use this as a starting checklist against the Standard Instrument definition. The applicable LEP or SEPP, and the specific design, decide the final answer.
| Building element | Usual treatment | Key qualification |
|---|---|---|
| Living areas, bedrooms, kitchens | Generally included | Above-ground, enclosed floor area |
| Bathrooms and laundries | Generally included above ground | In a basement or attic, may be excluded if not habitable |
| Internal corridors | Generally included | Open-air breezeways may be excluded if genuinely open to the weather |
| Shops, offices, commercial areas | Generally included | Expressly included even in a basement or attic |
| Mezzanine | Included | Expressly listed |
| Balcony or terrace | Depends | Excluded if outer walls are below 1.4 m; included if enclosed or closable. Some councils have specific wintergarden provisions |
| Void | Generally excluded | Must be a void above a floor at storey level |
| Common stairs and lifts | Generally excluded | “Common” means shared between occupancies |
| Private stairs and lifts | Generally included | Counting across levels varies between councils; confirm with the consent authority |
| Car parking | Depends | Excluded only to the extent it meets the consent authority’s requirements |
| Basement storage, access, garbage, services | Generally excluded | Area must be a “basement” as defined |
| Habitable room in a basement | Included | Expressly listed |
| Loading areas | Generally excluded | Loading and unloading of goods, including access |
| Plant room | Generally excluded | Used exclusively for mechanical services or ducting |
| Garbage room above a basement | Generally included | Only basement garbage areas are excluded |
Do Basements Count Towards GFA?
Some of a basement does, some doesn’t. First check that the space is a “basement” at all. Under the Standard Instrument, that means its floor is predominantly below existing ground level and the floor of the storey above is less than 1 m above existing ground level. A half-sunk level that rises above that line is not a basement, and the basement exclusions won’t apply.
Within a true basement:
- Excluded: storage, vehicular access, loading areas, garbage and services, plus required car parking and plant rooms.
- Included: habitable rooms, and any shop, auditorium, cinema and the like.
- Grey area: non-habitable rooms such as a laundry or bathroom. In some decisions, the Court has looked to the Building Code of Australia’s meaning of “habitable” and excluded a basement laundry, but councils don’t always agree.
A basement gym, office or home theatre will usually count. A basement bin room and storage cages usually won’t.
Does Car Parking Count Towards GFA?
Only the parking that meets the consent authority’s requirements is excluded, along with access to it. The test is the requirement, not the location:
- Required parking (from the DCP, SEPP or other control) is excluded, whether in a basement or above ground.
- Parking beyond the requirement has been held in some decisions to count as GFA.
- Where controls set a minimum (“at least”), the Court has accepted extra spaces in some cases. The outcome depends on how the control is worded.
- Motorbike parking required by the consent authority has, in some decisions, been treated as “car parking” and excluded.
- Access to the parking, such as aisles and corridors leading only to it, is excluded with it.
So check the parking rates in your council’s DCP or the relevant SEPP before you count a garage out. Some councils also publish the space dimensions they accept for the exclusion. A residential rule for one development type should not be assumed to apply to a commercial project.
Do Balconies, Terraces and Voids Count?
Balconies and terraces
The test is the height of the outer wall:
- Outer walls below 1.4 m, such as a balustrade: excluded.
- Fully enclosed, or enclosable with closable windows or louvres: included. Some Court decisions have treated wintergardens with closable glazing as GFA.
- Partly screened, for example permanently open louvres above a solid balustrade: often excluded, because the space stays open to the weather.
The design detail matters. A change from fixed to operable louvres can move a balcony into GFA. Some councils also have specific LEP or DCP provisions for wintergardens, so check the local controls before assuming how they will be treated.
Voids
A void is an opening through a floor, such as a double-height living room or atrium. At the upper level there is no floor to stand on, so the void is excluded. The floor below it still counts.
Do Stairs and Lifts Count?
It depends on whether they are common.
- Common vertical circulation (stairs and lifts shared between occupancies, such as in an apartment building or office) is excluded. Some Court decisions have also excluded the landings that form part of those common stairs.
- Private stairs and lifts inside a single dwelling or townhouse are not “common” and are generally included. Because the stair or lift shaft reads as a void at 1.4 m on alternate levels, how the stair and lift are counted across levels varies between councils, so confirm the approach with the consent authority.
- Lift towers and lift motor rooms used exclusively for services are excluded as plant.
GFA Calculation: A Simple Example
Illustrative example only. This is a hypothetical three-storey house to show the method, not a determination for any real DA.
Areas measured from the internal face of the external walls at 1.4 m above each floor:
- Ground floor: 220 m², including a 40 m² garage for two cars
- First floor: 200 m², including a 10 m² void over the entry
- Second floor: 180 m²
- A 20 m² balcony off the first floor, with a 1.0 m high balustrade
Step 1: Add up each floor. 220 + 200 + 180 = 600 m².
Step 2: Test each possible exclusion.
- Garage (40 m²): the council’s DCP requires two spaces for this dwelling, so the garage meets the requirement and is excluded. If the DCP required only one space, the second space would count.
- Void (10 m²): it is a void above a floor at storey level, so it is excluded.
- Balcony (20 m²): it sits outside the external walls and its outer wall is below 1.4 m, so it was never in the floor areas. Nothing to deduct, and nothing to add.
- Private stair: it sits inside a single dwelling, so it is not common circulation and stays in.
Step 3: Arrive at the GFA. 600 − 40 − 10 = 550 m².
If the balcony had closable glazing, it would be enclosed floor area and the GFA would rise to 570 m².
GFA vs Building Footprint vs NLA vs FSR
These terms are often mixed up. They measure different things:
- Site area: the land area used for planning calculations, worked out under the LEP’s site area rules.
- Building footprint: the ground area the building covers.
- GFA: the planning-defined floor area across all storeys, after inclusions and exclusions.
- NLA (net lettable area): the usable or lettable area under a property-industry method; not a planning measure.
- FSR: the ratio of GFA to site area.
A three-storey building can have a GFA far larger than its footprint, because GFA adds up every floor.
Planning GFA is also different from the GFA a quantity surveyor uses in a cost plan or EDC report. For costing, a QS measures building areas under the AIQS Australian Cost Management Manual, which follows its own rules (for example, measuring to the outside face of external walls). Archi-QS works with both, so the planning figure and the cost figure are each measured on the correct basis.
How GFA Affects FSR
Under the Standard Instrument, the floor space ratio of buildings on a site is the ratio of the GFA of all buildings within the site to the site area:
FSR = GFA ÷ site area
For example, a 1,200 m² GFA on a 2,000 m² site gives 1,200 ÷ 2,000 = 0.6:1.
Run the other way, the FSR tells you the maximum GFA: on that same 2,000 m² site with a 0.6:1 control, the most you can build is 1,200 m². That is why GFA sits at the start of every feasibility study and early-stage cost plan. Every square metre counted or excluded changes the yield.
Meeting the FSR does not guarantee approval. Height, setbacks, design quality and other controls still apply.
Why GFA Accuracy Matters for a DA
The GFA figure flows through the whole application. It affects:
- whether the proposal complies with the FSR development standard
- whether a written request to vary the standard is needed
- the development yield and project economics
- design decisions such as balcony treatment, basement layout and parking numbers
- the planning report and the council’s assessment
A wrong GFA can make a complying scheme look non-compliant, or the reverse. It does not automatically lead to refusal, but it can mean requests for information, redesign or a reduced yield late in the process.
GFA is also a separate calculation from the development’s cost. Both are prepared for the DA, and both need to be consistent with the same drawings: the Estimated Development Cost prices the works, while GFA measures the floor space.
What If Council Questions Your GFA?
Discrepancies are common. The architect’s area schedule, the planning report, consultant schedules and council’s own take-off can produce different numbers, especially on complex designs. Council may then ask for clarification, marked-up GFA diagrams or independent supporting evidence.
This is where a calculation and a validation differ:
- GFA calculation: working out the floor area under the applicable definition, usually by the architect or designer as part of the drawings.
- GFA validation: an independent review that checks the calculation against the plans and the definition, area by area, and confirms the result.
Archi-QS prepares Gross Floor Area Validation Reports for development applications. Archi-QS analyses the building plans and specifications to determine the total GFA, applying the inclusions and exclusions of the applicable definition area by area, and then uses the result to check the FSR against the site’s allowance.
When Do You Need a GFA Validation Report?
It is not required for every DA. It tends to be useful when:
- council has questioned or disputed the GFA
- the proposal sits close to the maximum FSR
- the design has complex areas such as wintergardens, breezeways, mezzanines or split-level basements
- different consultants have produced different figures
- council has specifically requested independent validation
Who Can Calculate GFA?
There is no rule that only a particular profession can calculate GFA. Architects, building designers, town planners and quantity surveyors all work with GFA calculations.
A quantity surveyor is often brought in where the figure needs independent checking: when FSR is tight, the design is complex, or council asks for validation. Measuring areas accurately from drawings is everyday work for a QS. For how GFA validation fits alongside other pre-DA reports, see our overview of pre-construction services.
FAQs
What is GFA in NSW?
Gross floor area is the planning-defined floor area of a building, used to test it against controls such as FSR. Most LEPs use the Standard Instrument definition.
How is GFA calculated for a DA?
Add up the floor area of each storey, measured from the internal face of external walls at 1.4 m above the floor. Then remove only the areas that meet one of the definition’s exclusions.
Is GFA measured internally or externally?
Internally. Under the Standard Instrument you measure to the internal face of the external walls, so wall thickness is not counted.
Why is GFA measured at 1.4 metres?
It fixes the height at which the wall face is read, so sloping or irregular walls are measured consistently rather than at the slab edge.
Does basement parking count towards GFA?
Parking that meets the consent authority’s requirements, and access to it, is excluded wherever it is located. Parking beyond the requirement can count.
Do balconies count towards GFA?
Not if their outer walls are less than 1.4 m high. Balconies that are enclosed, or can be closed with windows or louvres, generally count.
Are stairs and lifts included in GFA?
Common stairs and lifts shared between occupancies are excluded. Private stairs and lifts inside a single dwelling are generally included.
What is the difference between GFA and FSR?
GFA is an area in square metres. FSR is the ratio of GFA to site area, such as 0.6:1.
Do I need a QS to verify my GFA?
Not as a rule. A quantity surveyor’s validation is useful where council questions the figure, FSR is tight or the design is complex.
Conclusion
Calculating GFA for a NSW DA comes down to applying a written definition to real drawings: measure each floor inside the external walls at 1.4 m, include what the definition includes, and exclude only what genuinely meets an exclusion. The tricky elements are basements, parking, balconies, voids and stairs, where the outcome depends on the design detail and the wording of the control.
Check the instrument that applies. The Standard Instrument provides the general NSW framework, but the applicable LEP, SEPP or other instrument governs your site. For example, the Housing SEPP has its own provisions for seniors housing, and the Codes SEPP uses its own definition for some complying development.
If your proposal is close to the permitted FSR, has been questioned by council, or has areas that are hard to classify, an independent GFA validation can give you a clear, area-by-area answer. Contact Archi-QS with your plans to discuss a validation report.