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Granny Flat Land Size Requirements – With Real Examples

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To build a granny flat on your property, there are many rules. One of the most important is the minimum size that your land must be. So, what is the land size required for a granny flat?


The land size required is mainly impacted by your local Council. However, a good regulation to stick to is a minimum of 450sqm. Understanding that there are other restrictions which must be met for larger parcels of land.


I will talk about whether there are exceptions to the rules for land size requirements. Such as, whether different Councils’ have different land size requirements.


DON'T PAY A FORTUNE FOR YOUR GRANNY FLAT. Find out how to deal with council and build a granny flat for the lowest cost possible. Learn More.

Or, whether sloping blocks or flood zones have different regulations.


Lastly, I will discuss whether you can convert an existing dwelling on a smaller block of land into a granny flat.


Are There Exceptions to the Rules for Land Size Requirements?


Simply put – no. Only two dwelling are allowed on one property.


The regulations for land size requirements are part of the State Environmental Planning Policy (SEPP).


Under SEPP, if you have a:


  • Residential property larger than 450sqm with a minimum 12m street frontage, the you are allowed to build a granny flat.


However, regulations including setbacks increase with the size of the property. These are shown in the table below:


Lot Size Total Floor Area Landscaped Area Minimum Frontage Site Coverage Building Height Front Setback* Side Setback Rear Setback
450 – 600 sqm 330m2 20% 12m 50% 8.5m 4.5m 0.9m 3m
600 – 900 sqm 380m2 25% 12m 50% 8.5m 4.5m 0.9m 3m
900 – 1500 sqm 430m2 35% 15m 40% 8.5m 6.5m 1.5m 5m
1500 sqm or more 430m2 45% 18m 30% 8.5m 10m 2.5m 10m

*Non-classified road


Can You Build a Granny Flat on Rural Land?


There are a lot of rules surrounding building granny flats on rural land. To answer to this question, you first need to answer some questions about your property:


  • Is the land unsewered? If there is no sewer connection, the lot size and capacity for on-site effluent disposal may restrict development.

Meaning, building a granny flat will not be approved.


  • Is the land unoccupied? Granny flats cannot be built on unoccupied land.

That is, there must be a primary home on the land for the granny flat to be approved.


  • Are there other factors affecting the land? Rural land is more likely to be subject to environmental agreements such as biobanking.

So, there may be development restrictions on your land, and you will not be approved to build a granny flat.


To find out whether your rural land is going to be approved for a granny flat, the first thing to do is contact your local Council. For a small fee, your Council can provide you with a copy of your Section 10.7 (formerly known as the Section 149) Certificate.


This document contains information on any restrictions on development on your property. For the steps to take it is important to understand the process of Council Approval for Granny Flats.


Do Different Councils Have Different Land Size Requirements?


Yes – the minimum land size needed to build a granny flat can actually vary from Council to Council.


A good guide is to run by is at that you’ll need a minimum of a 450 square metre block of land. But there is no harm in walking directly up to the office of your local Council and asking them.


Do Sloping Blocks or Flood Zones Have Different Requirements on Land Size?


There are no different regulations for building on sloping blocks. Although, it does make the approval process a bit trickier.


If building a granny flat on a site that has a noticeable slope, you just need to put more thought into your design. Plus you must be mindful of height restrictions and how this will impact the approval process for your secondary dwelling.


Typical problems for steep sites include:


  • Roofwater Drainage – There are regulations on drainage and granny flats in SEPP.

It states that all stormwater collecting must be transferred by a gravity-fed or charged system to either;

  • A public drainage system
  • An on-site disposal system, or
  • An inter-allotment drainage system

Meaning, if your property slopes forwards, you can connect your roofwater drainage to the closest drainpipe. If your property slopes towards the rear, you can connect to a Drainage Easement (if there is one).

Drainage Easements are simple to connect to, but unfortunately uncommon.


Another option is to dig a trench, creating an ‘on-site disposal system’, also known as:


  • On-site dispersion systems
  • Rubble pits, or
  • Dispersion pits

They are usually 4m in length, 0.6m in width and 0.6m in depth. However, they come with strict regulations;


  • They must be placed at the bottom of the granny flat
  • They must be a minimum of 3m from any other structures, boundaries and tree-trunks


So, you have to allow room in your design for an on-site disposal site, if one is required.


  • Sewer Mains – This topic can be complicated.

The ‘Sewer Mains’ is the ‘Board’s Sewer’. You have a private line which runs from your house to the Sewer Mains’ itself. Of course, you can use your private sewer line for your granny flat – that pipe is yours. Unfortunately, many properties that slope to the rear have a Sewer Mains running through their front yard.


So, you may also need to get separate approval from the water corporation to build. A way of doing so is to show your development plans to a Sydney Water Quick-Check Agent.


To gain approval, your plans need to ensure you are going to avoid and/or protect the sewer. You may want to enlist the assistance of a Civil Engineer if you plan on building:

  • Within 600mm of the sewer
  • 1 or 2 times the sewer’s depth


However, the easiest (and cheapest) option is completely avoiding the sewer, if you have the room.


  • Heights vs. Setbacks – SEPP has regulations on many design requirements for granny flats, including Building Height.

The height of the building affects your setbacks (especially rear and side setbacks) as soon as the building exceeds 3.8m high.

Put simply, the building height is:


  • The vertical distance between the existing ground level, and
  • The highest point of the dwelling.


If building on sloping ground, the building height will increase more quickly than on flat ground. As such, your setbacks will increase at a faster rate. A way of lessening this impact of this is to take into account your roof type.


This too can be seen in my article on Granny Flat Height Restrictions.


As for building in a Flood Zone, there are no different requirements on land size. However, a different approval pathway may need to be taken depending upon how severe your case of flooding is.


Can an Existing Dwelling on the Land be “Converted” to a Granny Flat on the Title on Smaller Blocks?


Yes – it is possible to convert an existing garage or shed already on the site into a granny flat. For an example on how this is done, please see my blog “Detached Granny Flats – How To Do It Right”.


In this post above you will find all the information that you need to know about:

  • Regulations for conversions
  • Costs to convert a dwelling




A general guideline for the minimum land size required to build a granny flat is 450sqm. However, this can vary from Council to Council.


So, if you have a smaller property and want to build a granny flat, it won’t hurt to ask your local Council their regulations. Or, if you have a smaller block, you can convert an existing dwelling already on site, such as a garage or shed, into a granny flat.


Other than this, there are no exceptions to the rules for land size requirements. Only two dwelling are allowed per property, and setbacks apply as per the size of the lot. When it comes to building a granny flat on rural land, it is best to find out your restrictions first.


You can do so by asking your Council for a copy of your Section 10.7 Certificate. Rural land is more likely to be subject to development restrictions (i.e. biobanking), and you will find this information in this Certificate.


The land must also be sewered and already have an existing home. If building a granny flat on sloping property, you may have to put more thought into your design.


This is due to typical problems such as:


  • Roofwater Drainage
  • Sewer Mains
  • Heights versus Setbacks


If building in a flood zone, your may have to put more time into your approval process. A different approval pathway may need to be taken if you have a severe case of flooding on your property.


So, don’t let size, slopes or flood zones stop you from designing your granny flat – just do your research first.