Granny Flats FAQs

1. How long will it take to get approval before we can start building a granny flat?

It usually takes approximately 6-8 weeks to gain Complying Development Approval. It is important to keep in mind that each property is different and in turn are assessed individually under the State Environmental Planning Policy, also known as the SEPP.

2. Do we have to gain approval from our local council to build a granny flat or can it be done through a private certifier?

Private certifiers have authority to assess and approve the construction of granny flats. The benefit of gaining approval through a private certifier is that the process is much quicker than submitting documents through a local council. Once your granny flat is approved, the documents are still sent over to your local council for their records.

3. What is a Private Certifier?

Private certifiers are qualified and professional entities that are entitled to issue approval and permits for construction proposals, either residential or commercial.

4. Do all councils in Sydney allow Granny flats?

Yes. However, you will need to check with your local council to see if there are any restrictions, which may prevent a granny flat being built on your block. This is usually highlighted in the 10.7 Planning certificate (formally known as a 149 Planning certificate) that can be purchased from your local council. This document can also be located in the contract of sale of the property.

5. Do I have to use an Inhouse Granny Flats standard design?

No. At Inhouse Granny Flats we specialise in custom designed granny flats to suit your property, however we also have over 2000 floor plan designs that you can select from. You will have the opportunity to sit with our design team to put together a concept.

6. What is the maximum size granny flat I can build?

The maximum size for a granny flat, built as a secondary dwelling, is 60 m2. An attached garage with a roller door can also be constructed.

7. Are there any guidelines I need to meet when building a granny flat on my property?

Yes. All guidelines must comply with the current legislation which is called the Affordable Rental Housing State Environmental Planning Policy 2009, otherwise known as the ‘SEPP’. We can talk further about your property if we need to do a DA Approval.
If you comply under a CDC approval and your property is 450m2 the setbacks for a granny flat need to be:

  • 3 metres from the rear fence
  • 0.9 metres from the side fence
8. Can I attach a granny flat to my house?

Yes. However, extra measures will need to be taken in consideration to ensure that proper fire-rated walls are built between the connecting walls.

9. Are there any hidden costs with Inhouse Granny Flat Builders?

No. We pride ourselves on no hidden costs at Inhouse Granny Flats. We provide a fixed price quote after we have completed a free site inspection on your property. Any additional costs that are not included are specified in our tender. This is our guarantee to you.

Construction FAQs

1. Can I build on a concrete slab or steel piers?

You can build a granny flat on either a concrete slab or steel piers. At Inhouse Granny Flats, our preferred method of construction is concrete slab on ground. However, some properties are unable to use this option when they’re within a flood zone or if the property is on a large slope.

2. Do I get a choice in the colors and finishes of my granny flat?

Yes. We have a large range of suppliers, colours and materials for you to choose from in our own Sydney showroom. At Inhouse, we understand the overwhelming nature of building your first project. So that’s why we offer you our expertise and guidance during the material selection stage.

3. Are your granny flats prefabricated kit homes?

No, our granny flats are permanent structures. At Inhouse Granny Flats, we specialise in building custom designed homes that are cut and constructed on site by fully licensed and qualified tradesmen.

4. Do you need access to the main water, gas and electricity?

Yes. Granny flats are built using the existing dwelling’s services during construction. If there are tenants in the main property, they will only be minimally affected.

All services to the granny flat are supplied and handed over with separate metering. It will make it easier to organise and differentiate services bills if the granny flat is being rented out.

5. How long does the granny flat construction process take?

Generally it takes 12 -14 weeks for your granny flat to be built from start to completion. This is also subject to weather and other unforeseen circumstances.

6. When can I rent out my granny flat?

Granny flats can only be rented out once the private certifying authority has issued the final occupancy certificate.

7. Are there insurances that cover me?

Yes. All building approvals come provided with a seven-year structural home owners warranty on your granny flat.

Duplexes FAQs

1. What is the official name of the new SEPP (now commonly referred to as the new Medium Density Housing Code)?

State Environmental Planning Policy (Exempt and Complying Development Codes) Amendment (Low Rise Medium Density) 2017.

2. What date is recorded as the official commencement date for this new SEPP?

6th July 2018

3. How much will the knock down of my existing home and construction of a 450m2 Duplex typically cost on a reasonably level block of land?

Approximately $780k -$790k including GST, but could be more depending on demolition and site costs and any upgrades selected.

4. Can a Private Certifier approve all of the work including knock down, construction and re-zoning?

Yes, due to the certainty of the pre-existing R1, R2, R3, RU5 Zoning, in the vast majority of cases. Exceptions will be Heritage Listed properties, (or those in heritage Conservation areas), Terrace homes in Bushfire affected areas and those lots situated on flood affected sites or sites where storm water management can’t be effected to accord with the Local Council’s hydraulic engineering plans.

In those cases a DA through Council can generally be successful if the approval-criteria is met. If a dwelling house is to sit closer than 9.0 m to a freeway boundary or under a flight path or upon land that has a Bush Fire Attack Level of 40 or higher, then generally it will be referred to Council as well.

At Inhouse, we deal with these matters every day and can advise or mentor you through this process without misconception. In cases where Council is unsure if they will support a lodged DA, we usually arrange a Pre DA Conference in advance of lodging, then attend with you and present the documents and floor plans etc to Council’s planning approvals team and engineers.

Council will then advise in advance what their exact requirements will be for approval. Unfortunately, development on Battle Axe blocks will need to approved through the DA process and un-sewered land and land not connected to AUSGRID (electricity) would also need to be referred to Council, however the incidence of these lots arising would be very low in the zonings that apply to this SEPP.

5. Does the new Medium Density Code override the Council’s LEP?

No, the LEPs have been amended to include the new code. However, the new Code overrides Council’s Development Control Plans. And any approvals by a Consent Authority for a builder to construct under the new Housing Code must follow the design guidelines which accompany the new code. These guidelines cover many aspects such as private open spaces and amenities. And despite the increased density, it’s expected that this will improve the streetscape and give people better accommodation options.

6. What sort of site costs might make my project more expensive?

There is often a need to remove trees and large tree roots, sheds, garages, swimming pools and the like. If the land has been previously filled or you have insufficient power coming into your site to power two homes, or a steep fall over the site, or significant storm water drainage issues, these will increase the costs.

7. Will Subdivision be automatically permissible, once the project is completed?

At the time of writing this material, there are only a handful of Councils who prohibit sub-division of medium density dwellings. Blacktown Council require corner blocks with 300m² minimum residual lots to be produced before subdivision will be permitted. Hills Shire Council prohibit subdivision of all Dual Occupancy development.


  • 3 metres from the rear fence
  • 1 metre from both the side fences
8. Are there any hidden costs with Inhouse Property Solutions?

There are no hidden costs at Inhouse. Once we prepare your fee proposal, the total amount for the whole project is clearly outlined. Anything not included as standard is highlighted in red. At Inhouse, we guarantee that.

the process

  • 1. Getting a Quote

    1. Getting a Quote

    The first step to building a granny flat is an enquiry. When you call or email us, we will send you a free information pack so you get a better understanding of what we do. From there, our qualified builder will inspect your backyard free of charge to check the area and discuss your needs and requirements. Our sales representative will then send you a fee proposal, which outlines the necessary requirements for your granny flat as well as its inclusions and overall price.

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  • 2. Flats and drawing stage

    2. Flats and drawing stage

    Once you have accepted the terms and conditions of our fee proposal, provided us with a 10.7 planning certificate (formally known as 149 Certificate) from council, a sewer diagram and you have paid a deposit, we will organise for a surveyor to carry out a site survey on your property.
    Once we have received your survey our qualified Inhouse design team will then draw up a concept floor plan and organise a personalised meeting to sit down with you to ensure your needs are met and any design alterations are made.
    Once you are happy, we will proceed to start your approval with a private certifier or via council.

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  • 3. Contracts

    3. Contracts

    Once your completed approval has been issued by a Private Certifier or Council, we will ask you to sign a Fair Trading Home Building Contract and organise your Home Owner’s Warranty. We will invite you in for a meeting to select all the materials and colours for your granny flat from our wide range of selections available in our showroom.

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  • 4. Construction

    4. Construction

    We will schedule your project to start and order all materials you have selected for the build.
    We will then be on-site organising earthworks, excavation and piering to prepare for the slab.
    You will be appointed a site foreman who will guide and update you throughout the construction until the handover is complete.
    At Inhouse, we know that this investment is important to you and we do our best to finish construction as soon as possible while not compromising the quality of your building. Your brand new granny flat will be completed within 12 -16 weeks.

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