Guide
Knockdown rebuild and duplex finance Perth
Building a duplex on your block is one of the stronger plays for Perth property investors right now. Under the 2027 negative gearing rules, a knockdown rebuild that creates multiple dwellings is one of the specific new build types that keeps full negative gearing treatment. A single house rebuild does not. The finance is more involved than a standard construction loan. This guide covers what qualifies, how the loan works and how to use land equity to fund the build.
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The 2027 rule that matters here: a knockdown rebuild qualifies as a new build only if it creates multiple dwellings. Build one house to replace one house and it does not qualify. Build a duplex to replace one house and it does. Confirm your project with your accountant before signing a building contract.
What the 2027 rules say about knockdown rebuilds
The negative gearing changes announced in the 2026-27 Federal Budget limit the offset of rental losses against wages to new builds for residential properties purchased after 12 May 2026, from 1 July 2027. The legislation has not yet passed but the draft is specific about what qualifies.
Knockdown rebuilds are on the qualifying list, with a condition: the rebuild must create multiple dwellings. A single house demolished and replaced by one new house is explicitly excluded. The rationale is housing supply. The exemption is designed to encourage projects that add dwellings to the market, not just replace them one for one.
What this means practically for Perth investors:
- Duplex build on a demolished site: qualifies. Two dwellings replace one. Full negative gearing treatment against wages maintained.
- Pair of townhouses on a demolished site: qualifies. Same reasoning as a duplex.
- Single house knockdown rebuild: does not qualify. One dwelling replaces one. Treated as established for negative gearing purposes if purchased after budget night.
- Granny flat addition to existing home: does not qualify. An addition to an existing dwelling is not a new build under the rules.
How the finance works
The finance structure for a knockdown rebuild duplex depends on whether you already own the land or are buying it.
If you own the land
If the block is yours and has equity, the most common approach is an equity release combined with a construction loan. The lender values your land, releases equity up to roughly 80 percent of its value minus any existing debt, and that released amount funds the demolition costs and construction contribution. The construction loan then draws down progressively as the build proceeds: demolition first, then slab, frame, lockup, fitting out and practical completion. You pay interest only on what has been drawn during the build.
If you are buying land to rebuild
If the plan is to purchase a block specifically for the knockdown rebuild, the sequence is a standard land purchase followed by a construction facility. This is similar to a house and land package: the land settles first, then the construction loan activates. The demolition cost is additional to the build cost and needs to be in the total budget from the start. Lenders want a fixed price contract covering both demolition and construction rather than separate arrangements.
Knockdown rebuild duplex: key facts
| Qualifies under 2027 rules | Yes, if it creates multiple dwellings (duplex, townhouses) |
| Does NOT qualify | Single house replacing single house; granny flat additions |
| Funding if you own the land | Equity release + construction loan |
| Funding if buying land | Land purchase + construction facility (two-stage) |
| Interest during build | Charged on drawn funds only, not the full loan amount |
| Demolition cost | Included in the build contract budget from the start |
| DA requirement | Development approval or clear DA pathway required before full finance approval |
What lenders look at on a duplex build
Duplex and dual occupancy projects are assessed more cautiously than single dwelling construction loans. The main additional considerations:
- Development approval. Most lenders want DA in place, or at minimum strong evidence the project is approvable under the local planning scheme, before issuing full construction approval. A broker can tell you which lenders are more flexible on DA timing and which require it upfront.
- Zoning and block suitability. The block needs to allow for two dwellings under the applicable planning scheme. In Perth, residential zoning codes such as R30, R40 and R60 determine what density is permitted on a given lot. A density zoning that supports duplex development makes lender approval more straightforward.
- Fixed price contract from an experienced builder. Lenders want a fixed price contract from a registered builder who has completed multi-dwelling projects. Cost-plus contracts are generally declined or heavily restricted. Builder experience with duplex or dual occupancy projects is assessed, not assumed.
- LVR limits. Some lenders cap their LVR on multi-dwelling construction loans more tightly than on single dwelling builds. 70 to 80 percent is a common ceiling; going above that generally requires a lender specifically comfortable with duplex projects.
Lender selection matters more on a duplex build than on a standard construction loan. The broker's job is to match the project to a lender whose duplex policy fits before the application goes in, which avoids wasted credit enquiries and avoidable delays.
Frequently asked questions
Does a knockdown rebuild qualify for negative gearing under the 2027 rules?
It depends on what you build. A knockdown rebuild qualifies as a new build only when it creates multiple dwellings, such as a duplex or pair of townhouses. A single house demolished and replaced by a single new house does not qualify and is treated as an established property under the announced rules. Confirm your project with your accountant before committing to a builder contract, as the legislation has not yet passed Parliament.
How does finance work for a knockdown rebuild duplex?
If you own the land, a lender releases equity in the block and combines it with a construction loan that draws down in stages across the build. If you are buying land to demolish, the land settles first and the construction facility activates after. The construction loan covers demolition and build, drawing down progressively: slab, frame, lockup, fixing and practical completion. You pay interest only on what has been drawn during the build, and the loan converts to principal and interest at completion.
Can I use the equity in my land to fund the build?
Yes. If your block has equity, a lender can release a portion of it to fund the deposit or construction contribution. Usable equity is roughly 80 percent of the land's current value minus what you owe on it. Whether the equity release is sufficient depends on the build cost, the lender's LVR limits on duplex construction and whether your income supports both the existing debt and the new construction loan through to completion.
What do lenders look at differently for a duplex build?
Lenders assess development approval or approvability, zoning suitability for two dwellings, builder registration and experience with multi-dwelling projects, and a fixed price contract. LVR limits can be tighter than on single dwelling builds. Not every lender that writes standard construction loans will write duplex construction finance on the same terms, so lender selection is more critical here.
Do I need development approval before applying for finance?
You do not need DA in hand to begin the conversation, but most lenders require DA or strong evidence of approvability before issuing full construction approval. A broker who works with multi-dwelling projects can tell you which lenders are more flexible on DA timing and what documentation to have ready so you are not applying to a lender who will stall at a document you have not yet obtained.
General information only and does not consider your objectives, financial situation or needs. Tax outcomes depend on your circumstances: confirm the eligibility of your project with a registered tax agent or accountant before signing any building contract. Lending criteria, terms and conditions apply.
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