A knock-down rebuild in Sydney can be approved as complying development (a CDC issued by a certifier) if the demolition and the new house meet every standard in the Housing Code under the Codes SEPP and the lot carries none of the exclusions. If any standard is missed, or the land is heritage listed, in a heritage conservation area, a flood control lot, or affected by certain bushfire or environmental constraints, the project needs a development application, and the Statement of Environmental Effects (SEE) must then cover demolition, the new dwelling against the LEP and DCP, amenity impacts on neighbours, trees, stormwater and the section 4.15 matters. Choosing the pathway correctly at the start is the single biggest decision in the project.
Key takeaways
- The Housing Code lets a certifier approve demolition and a new one or two storey house on most residential lots, but every standard must be met, with no merit judgement available.
- A DA is the only option where the lot is heritage affected, is a flood control lot, or where a setback, height, site coverage or landscaped area standard cannot be met.
- Council DCPs often allow more flexibility than the code, which is why a DA sometimes produces the better house even when a CDC is available.
- The SEE for a knock-down rebuild must address the demolition, the streetscape change and the neighbours’ amenity as well as the new house itself.
- A DA usually takes 2 to 4 months in Sydney; a CDC is measured in weeks, but only if the design fits the code without exception.
How the two pathways work for a rebuild
Complying development is a combined planning and building approval issued against fixed standards. The NSW Planning complying development page describes it. For a knock-down rebuild the demolition of the existing house can usually be certified under the Codes SEPP, and the new house is then assessed under the Housing Code (or the Greenfield Housing Code in the nominated release areas). The certifier checks lot size, lot width, setbacks, height, site coverage, landscaped area, private open space, parking, earthworks and a list of site exclusions. There is no notification and no merit assessment.
A DA goes to council and is assessed on merit under section 4.15 of the Environmental Planning and Assessment Act 1979. Council applies its LEP and DCP, notifies neighbours, and can approve a departure from a DCP control if the objective is still met. It takes longer, but it allows a design that the code cannot.
DA or CDC: the comparison for a Sydney rebuild
| Question | CDC under the Housing Code | DA to council |
|---|---|---|
| Who approves it | Accredited certifier or council as certifier | Council planner, or a local planning panel in some cases |
| Standards applied | Fixed numeric standards in the Codes SEPP | LEP development standards plus DCP controls, with merit assessment |
| Heritage, flood control lots, some bushfire and environmental constraints | Excluded from the code | Assessed with specialist reports |
| Neighbour notification | None (a notice of intention only) | Yes, under the council’s community participation plan |
| Flexibility | None, every standard must be met | Departures can be justified against objectives |
| Typical timeframe | Weeks | 2 to 4 months for a house |
| Statement of Environmental Effects | Not required | Required |
The site checks that decide the pathway
Before any design work, our planners run the site through the constraints that knock a rebuild out of the code. Most are visible on the section 10.7(2) planning certificate and the NSW Planning Portal Spatial Viewer.
- Heritage. A listed item or a heritage conservation area under the LEP removes the CDC option for the new house. Parts of Parramatta, Windsor, Camden township, Campbelltown and the older Hills villages are affected.
- Flood. Flood control lots are excluded from the Housing Code. Large areas of Penrith, Hawkesbury, Fairfield, Liverpool and Canterbury-Bankstown are mapped, and the council’s flood information decides whether the lot is a flood control lot or merely flood affected.
- Bushfire. Bushfire prone land is not excluded outright, but the code limits the bushfire attack level at which a CDC can be issued and imposes construction requirements under AS 3959:2018. Sites on the edges of the Hills, Hornsby, Wollondilly and the Blue Mountains often need a DA.
- Lot geometry. The code sets minimum lot sizes and widths and scales setbacks and site coverage to the lot. Narrow or irregular lots in Granville, Auburn, Lakemba and Cabramatta frequently fail one line of the table.
- Slope and earthworks. The code limits cut and fill depths. Steep sites in Castle Hill, Kellyville, Winston Hills and along the Georges River often exceed them.
- Trees and biodiversity. The code cannot authorise removal of a tree that council protects, and land on the biodiversity values map is excluded.
If the site passes every check and the client is happy with a code-compliant house, we recommend the CDC. If it fails one check, or the client wants a design the code will not permit (a larger footprint, a reduced rear setback, a higher ceiling), the DA is the pathway and the SEE becomes the central document. Our DA or CDC pathway advice puts this in writing before drawings are commissioned.
What the SEE has to cover for a knock-down rebuild DA
Demolition
The SEE should describe the existing dwelling, confirm it is not a heritage item and not within a conservation area, address any asbestos with reference to a demolition work plan, and note the tree protection measures during demolition. On older housing stock in Blacktown, Fairfield and Cumberland, asbestos is assumed until a survey says otherwise.
The new dwelling against the LEP
Height of buildings measured from existing ground level, floor space ratio where the LEP applies one to houses, heritage, flood planning and earthworks clauses. Where a standard is exceeded, a clause 4.6 request is a separate document.
The DCP compliance table
Setbacks, site coverage, landscaped area, private open space, solar access, privacy, parking, cut and fill, fencing and streetscape, each with the requirement and the proposal side by side. The numbers come from the DCP for that council: The Hills DCP 2012, Parramatta DCP 2023, Canterbury-Bankstown DCP 2023 or whichever applies. A rebuild is often larger than the house it replaces, so the streetscape section matters more than it does for an addition.
Amenity
Shadow diagrams at 9am, 12 noon and 3pm on 21 June for a two-storey rebuild, with the hours of sun to each neighbour stated. Privacy treatment for every upper-level window and balcony on the side and rear elevations. Neighbours notice when a single storey cottage becomes a two-storey house, and the SEE should show the design has considered them.
Stormwater, trees and reports
The discharge point, on-site detention where the council requires it, an arborist report to AS 4970-2009 for any tree affected, and a summary of the BASIX certificate, survey, and any flood, bushfire or geotechnical report lodged with the DA.
Where rebuilds go wrong in the Hills and the inner west
- Designing for the DCP and lodging as a CDC. A house drawn to The Hills DCP 2012 setbacks will not necessarily meet the Housing Code, and the certifier has no discretion.
- Measuring height from finished ground. Height under the LEP is measured from existing ground level. On a site with fill, the difference can be half a metre.
- Forgetting the demolition consent. A DA for the new house must include the demolition. A CDC for the new house needs the demolition certified as well.
Frequently asked questions
Can a knock-down rebuild be done as complying development?
Yes, on most residential lots in Sydney, if the demolition and the new house meet every standard in the Housing Code and none of the site exclusions apply. Heritage, flood control lots and some bushfire and environmental constraints rule it out.
Do I need a Statement of Environmental Effects for a knock-down rebuild?
Only if the project goes to council as a DA. A CDC does not need a SEE, but it does need full compliance with the code and a complete set of certifier documents.
Is a DA or a CDC cheaper for a rebuild?
A CDC usually costs less in fees and time because there is no council assessment or notification. A DA costs more but can approve a house the code will not, which on a constrained or valuable lot may be worth far more than the difference in fees.
Can I demolish the old house before the approval?
Not without a separate approval. Demolition is development and needs either a CDC or a DA. Demolishing first can also remove evidence council needs, such as existing setbacks used to set the new front setback.
URBA advises on the pathway for knock-down rebuilds across Sydney and prepares the Statement of Environmental Effects when a DA is the right route, with particular experience in the Hills, Parramatta and the inner west. Send us the address and your brief and we will provide a fee proposal.