So you have a block of land, whether it’s your existing home that you are looking at demolishing or have an already vacant block of land; and you are looking at building a brand new home on it.  What’s the maximum size home can you fit?

This question has no simple and straight answer – it simply depends!  In this blog, I will attempt to give you a good (as much as possible) guide on how you can determine the maximum home size that you can potentially fit in your block.

Please note that there are other controls (like setbacks, private open space, etc…) that I will not take into account here as I want to do the house size exercise in isolation.

CDC vs. DA

The first step you need to take is to decide if you are going to be using CDC or DA for your project.  State Policies apply to any block regardless of it’s location.  This is subject to:

Remember, I am only talking about the great state of NSW :).   To get a bit more understanding about the difference between Local and State rules and their respective processes, please visit my blog on DA vs. CDC.

When you do obtain your reports, it will state whether you are allowed to use the SEPP or not.  Instances where you may not be able to use the SEPP include (but not limited to):

  • severely flood affected land
  • bushfire affected land
  • heritage restrictions on your block
  • building duplexes (at the time of writing this blog)
  • apartments
  • childcares
  • etc…

Your Section 10.7 Planning Certificate Certificate might contain some of the following examples:


For the sake of the exercise, let’s assume that you are allowed to use either one of them.  So which is betterThe short answer is neither.  It depends on your requirements, objectives and what you are trying to accomplish.  Regardless, your builder should always give you the option (if available) so you can make a more informed decision.

SEPP is relatively simpler in the way that it applies across the board so doing it over and over again for every block makes for an easier process from your builder’s perspective.  It reduces their cost and they in turn pass these savings on to you as their client.

The simplest way to think of the SEPP is like a list of checkboxes – if you tick them all then you will obtain your plans approvals.  If you miss a box, then you don’t.  There is no argument or discussion about any exceptions or variations etc…  You either meet the requirements or you don’t.

You can obtain your CDC approval through a private certifier or council which takes about 2 weeks (this does not include all the preparation work).


LEP / DCP on the other hand requires a lot more work.  Every local council has their own rules and guidelines.  For example:  you cannot apply Camden DCP to a home that you are building in Box Hill.  So your builder will have to go through the specific local council guidelines and the DA process (which can take months sometimes) to obtain your plan approvals.  This process cannot be done via a private certifier.

DA is also a merit based system, so you may be able to argue or have a variation approved from council even if it falls outside the guidelines, but this is subject to council’s discretion.

The DA Process also has 2 stage:

  1. Obtaining DA approval from Council
  2. Obtain CC (construction certificate) from the Private Certifier or Council

This is unlike the CDC process of course.

Which One?

One of the most common comments I always get is:  I want the biggest house possible.  There is no fast and hard rule about which guideline will provide you with a bigger house size.  You will just need to check both the SEPP & LEP / DCP that are applicable to your particular block of land and compare which pathway would give you the bigger size home (provided you are allowed to use either one of them).


So how much house can you fit?  Let’s look at Gross Floor Area (using the SEPP) vs. Floor Space Ratio (using the LEP / DCP).  Please remember that there is a number of other controls (like setbacks, private open space, etc…) that I will not take into account here.

That way we can grasp a deeper understanding of how this is calculated using different rules.  Please note that just because you are allowed to build a 250sqm house does not mean that you can.  This is because there are other applicable controls which may affect the home size, design, etc…

Gross Floor Area (GFA)

Let’s assume your block size is 400 square meters.  Here is the formula that you can use to find your Gross Floor Area (GFA):

GFA = 25% of lot area + 150 sqm

So in this instance, your GFA = (25 x 400) / 100 + 150 = 250 sqm

The official definition for Gross Floor Area can be found here.  Please note that the above formula is from the General Housing Code.  There are different formulas that apply to the Greenfield Housing Code.


Please note that this is not my design and I am using it for illustration purposes only.

  • the red line measures the area from the internal walls
  • deduct the size of the stairs and 1 x parking space
  • patios, Alfrescos, balconies, etc… are also excluded

As per the above diagram, the total gross floor area of your new home less the abovementioned exclusions should be equal to or less than 250sqm.  This means that you can fit a bigger house but the gross floor area of this bigger house cannot exceed 250sqm.

So the total area for the house can be 300sqm, but the gross floor area cannot exceed 250sqm.  The 300sqm consists of the 250sqm plus patio, alfresco, stairs, etc…

Floor Space Ratio (FSR)

Let’s again use similar assumptions and use your 400sqm block size.  So what’s the formula for Floor Space Ratio?

This varies from council to council.  Some councils don’t even have an FSR so you will have to satisfy all the other controls.  You may appreciate how difficult it is for your builder to tell you straight up what you can or cannot do in every single council.

So let’s assume there is an FSR formula and it’s ABC Council with it’s floor space ratio (according to their guidelines) being 50%.  Here is the formula:

FSA = 50% of lot area

So in this instance, your FSA= (50 x 400) / 100 = 200 sqm

Now ABC Council may have a different FSR definition compared to XYZ Council.  So you will need to go to that council’s website and find their local DCP / LEP; to make sure that you

  1. understand what’s included and what is not in the FSR calculation and
  2. how that applies to your particular design etc…

Given that there a large number of councils out there, I thought listing all of them here would be an overkill.  However if you have any questions or you are not sure, always contact me and send me a question with what you need to know and I will be more than happy to point you in the right direction.

A Note

So what’s the biggest size home can you fit in your block?  Here are some questions that will help you answer this question:

  • Which pathway will I use?  CDC vs. DA?
  • What guidelines apply to my block?
  • Are there any other controls that will affect the size of my new home?
    • For example:  setbacks, avoiding building over easements (preferable but subjective), private open space, etc…
  • What areas do I need to exclude from and include in my area calculation?
  •  Are there any other considerations that I need to take into account?
  • Which builder will I trust to give me the right information?

Please note that you can have 2 designs (38sq and 39sq); and both may have the exact the same Gross Floor Area.  This might be due to a bigger alfresco, different building material, bigger patio, etc…

Useful Links

Here are some websites that you may find useful.  Please note that I am not responsible for the content and you should always obtain professional advice and conduct your own due diligence at your own risk :).

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