How do I calculate floor space ratio of my development?

The floor space ratio is a development standard which is referenced in clauses 4.4 and 4.5 of Mosman LEP 2012 and controls the bulk and scale of buildings.

To calculate the floor space ratio for your development you will need to know:

  1. The site area
  2. The allowable floor space ratio for the site which is identified on the Floor Space Ratio Map
  3. The gross floor area of the development (this is defined in the Dictionary of Mosman LEP 2012)

The floor space ratio is the ratio of the gross floor area of a development to the site area expressed as a factor of 1. That is, the total floor area on all levels of the building minus any exclusions provided for in the definition of gross floor area, divided by the site area.

For example:

site area – 600m2
gross floor area – 300m2
calculation – 300m2 divided by 600m2 = 0.5
This provides for a floor space ratio of 0.5:1

It should be noted that the definition of gross floor area allows for the exclusion of car parking to meet any requirements of Council. Part 5.10 of Mosman’s Residential DCP specifies that for dwelling houses, a minimum of 1 space is required. Contact Council’s Duty Planner on 9978 4172 to discuss the specifics of your proposal as necessary.


16 Responses to How do I calculate floor space ratio of my development?
  1. Peter Dally
    05/01/2012 at 2:41 pm

    For 2012 residential applications is the FSR measured using the Draft Mosman LEP2011 – IE GFA measured tio the inner face of external walls?

    If an existing rear garage is reduced in size and used a bike shed is it considered as part of the FSR?

    If an existing garage is made inaccessable is it considered as part of the FSR?

    Is an internal stair void part included as floort space as there is no floor in the void?


    • The Mosman LEP 2012 (the LEP) comes into effect on 1 February 2012. From that date, all applications will be assessed against the LEP, including the definition of Gross Floor Area (GFA) and calculation of FSR in the LEP.

      An internal stair void is not included in GFA calculations, as the definition of GFA excludes “voids above a floor at the level of a storey or storey above”.

      Car parking, including access to that carparking, to meet the requirements of Council, is excluded from GFA. Council’s parking requirements are outlined in the relevant Development Control Plans.

  2. Are outdoor balconies or patios included in the GFA ?

    • The definition of gross floor area (GFA) specifically excludes balconies and patios from the GFA provided that the outer wall is less than 1.4m high

  3. how to i calculate of how many car park lot should I cater for if the Gross Floor area is about 14000 m2

    • The amount of carparking required is related to the proposed use of the site. Carparking rates for various uses are found in the Transport, access and parking section of the relevant Development Control Plan (DCP) for the particular zone. The DCP’s can be found at –

  4. So if my floor apace ratio is 0.5.1 And the block size is 640 how much will I be able to build on and is the garage , voids ,balcony s included ?

  5. If your block size is 640m2, the total allowable floor space is 320m2. Carparking to meet Council requirements, voids and balconies are not included. Please refer to the definition of gross floor area in Mosman Local Environmental Plan 2012, which can be found at –

  6. Thank you
    I understand

  7. How do you interpret FSR >1 ? Does that mean for a FSR of 2 you can have 2000m2 of floor space over multiple levels on a 1000m2 site?

    • Hi Grant,

      Yes, that is correct. So when considering the calculation of FSR alone, if you have a 1000sqm site and the FSR control is 2:1, the controls allow you to accommodate 2000sqm of gross floor area on the site.


  8. Morwenna Burn
    04/06/2016 at 3:48 pm

    Hi There,
    We are adding a top floor to our property and wish to add in a rear first floor balcony. Is this included in our fsr?


    • Hi Morwenna,

      Balconies with outer walls less than 1.4 metres high are not included in the calculation of Gross Floor Area as per the definition of Gross Floor Area in Mosman LEP 2012.


  9. Hi
    I have a double garage and car port approx 40 m2 will this be included in the floor to space ratio calculation if I am planning a Reno


  10. My land is 660 m2, according to LEP, FSR falls in to 0.5 : 1 ratio, that means I can build on 330 m2 of land, if I am building 2 story house can I do 330 m2 ground floor and another 330 m2 of 1st floor ? and also are the out door living areas and swimming pool included in this FSR calculation ? Please advise

    • Hi Indi,

      Unfortunately with an FSR of 0.5:1, you cannot have 330sqm on the ground floor and another 330sqm on the first floor. Under Mosman LEP 2012, if your land is 660sqm and the FSR control is 0.5:1, the total Gross Floor Area allowed is 330sqm.

      Swimming Pools are not included in the calculation of Gross Floor Area as per the definition of Gross Floor Area in Mosman LEP 2012 (provided they are unenclosed). Swimming pools would be subject to a number of other controls in Mosman’s LEP and DCP.


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