FAQs – Duplexes


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.

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

6th July 2018

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.

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 In House 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.

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 guide lines cover many aspects such as private open space and amenity and despite the increased density are expected to improve the streetscape and give people improved accommodation options.

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.

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

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.

Construction FAQs

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 due to being within a flood zone or if the property is on a large slope. In this case, steel piers will be used at no additional cost.

Do I get a choice in the colors and finishes?

Yes. We have a large range of suppliers, colors 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.

Are there insurances that cover me?

Yes, All building approvals come provided with seven years structural home owners warranty on your dwelling.

Granny Flat Information Night