Is Your Block Suitable for a Knockdown Rebuild?

Is Your Block Suitable for a Knockdown Rebuild?

Not every block suits a knockdown rebuild equally. Some blocks are straightforward — flat, regular, well-serviced, no constraints. Others have challenges that add cost and complexity. Buildana (Lic. 487805C) has built KDRs across every major Western Sydney council area. Here is how we assess whether your block is KDR-ready.

Zoning — The First Check

Your block must be zoned for residential development. The most common zones for KDR in Western Sydney are:

• R2 Low Density Residential: the most common. Permits one dwelling per lot (and potentially dual occupancy under the July 2024 Low and Mid-Rise Housing Policy). Minimum lot size for a dwelling: typically 450 sqm across Fairfield, Liverpool, Cumberland and Blacktown, 500 sqm in parts of Canterbury-Bankstown.

• R3 Medium Density Residential: permits one or more dwellings per lot plus dual occupancy. Found in pockets near town centres and transport in Fairfield, Liverpool, Bankstown, Auburn, and Merrylands.

• R1 General Residential: permits residential development. Less common in established Western Sydney suburbs.

Check your zoning on the NSW Planning Portal (planningportal.nsw.gov.au) or contact your council. Buildana checks zoning as part of our free site assessment.

Important: being zoned residential does not guarantee you can build anything you want. The LEP also specifies height limits, floor space ratio (FSR), and minimum lot sizes that constrain what can be built.

Block Size, Shape, and Frontage

Size: Most KDRs in Western Sydney are on blocks of 450–700 sqm. Blocks under 450 sqm can accommodate a KDR but the home will be more compact and setbacks more constrained. Blocks over 700 sqm offer excellent design flexibility and may qualify for dual occupancy.

Frontage: The width of your block at the street determines how the home sits. Wider blocks (15m+ frontage) allow a generous facade with double garage, entry, and side access. Narrow blocks (under 12m) require a longer, narrower design — typically called a narrow lot design — with the garage dominating the front facade.

Shape: Regular blocks (rectangular or close to it) are the most efficient to build on. Irregular shapes — pie-shaped, battle-axe, or heavily tapered — require more creative design and may have less usable area.

Corner blocks: excellent for KDR. Dual street frontage allows the home to address both streets, with separate garage access from the secondary street. Corner blocks in Fairfield, Liverpool and Canterbury-Bankstown are some of the best KDR sites in Western Sydney.

Site Conditions That Add Cost

These site conditions do not prevent a KDR — but they add cost and complexity:

Slope: Flat to gentle (under 2m fall) is ideal. A fall of 2–4m across the building area adds $30,000–$80,000 for retaining walls, benching, and modified foundations (Rawlinson benchmarks).

Reactive soil: Class H (highly reactive) and E (extremely reactive) soils are common across Western Sydney's clay-heavy suburbs. These soils expand and contract with moisture changes, requiring engineered raft slab or pier foundations. Additional cost: $10,000–$30,000 over a standard waffle pod slab.

Rock: Sandstone and shale can be encountered during excavation. Rock removal costs $100–$250/cubic metre.

Flood-prone land: Parts of Fairfield (Prospect Creek), Liverpool (Georges River corridor), and Canterbury-Bankstown (Cooks River, Salt Pan Creek) are flood-affected. A KDR on flood-prone land requires DA (not CDC), flood-compatible design, and minimum floor levels. It is feasible but adds cost and timeline.

Contamination: Former industrial sites in suburbs like Villawood, Yennora, Smithfield, and parts of Granville may require contamination assessment. Remediation costs vary widely — $20,000–$100,000+.

Buildana identifies all site conditions at the free assessment stage. No surprises during construction. For the full KDR process, see our complete knockdown rebuild guide.

Constraints That May Prevent a KDR

These are the deal-breakers — conditions that can prevent a KDR entirely:

• Heritage listing: If the existing house is individually heritage-listed, demolition may not be permitted. Check the heritage schedule in your council's LEP.

• Heritage conservation area: Demolition in a conservation area requires DA and heritage assessment. Council may refuse demolition if the existing building contributes to the area's character. Affected suburbs include parts of Granville, Auburn, Lidcombe, and Bankstown Heights.

• Covenants on title: Some older subdivisions have restrictive covenants that limit building height, materials, or use. Check your Certificate of Title.

• Easements: Sewer, stormwater, and drainage easements prevent building over the easement alignment. This reduces the buildable area of the block.

• Severe contamination: Heavily contaminated sites (former service stations, industrial facilities) may cost more to remediate than the land is worth.

None of these assessments are difficult — but they need to be checked before you invest in design and documentation. Buildana's free site assessment covers all of these checks. Contact Buildana to book your assessment.