Granny Flat Loans: Broker Requirements

A granny flat loan funds a secondary dwelling on the same residential title as a main home. Assess the proposed use and approvals first, then match the contract, valuation and repayment capacity to a suitable funding route.

Existing home equity can support the borrowing, but it doesn’t remove the lender’s construction requirements. Proposed rent also needs its own assessment. A client who can repay only if the new dwelling earns rent needs a different funding analysis from one housing family rent-free.

Define the Secondary Dwelling

Record what the client intends to build, who will occupy it and how it relates to the main home. Include the address, title owner, proposed floor plan, permanent installation method and whether the main dwelling already exists or is also being built.

Ask whether the flat will house relatives, earn long-term rent or have another intended use. Record any payment the occupants will make and whether there will be a tenancy agreement. A family arrangement without rent doesn’t create rental income for the servicing calculation, which tests whether the client can meet repayments.

In New South Wales, the planning department’s secondary-dwelling guidance defines a granny flat as self-contained accommodation within, attached to or separate from another dwelling on the same site. Its page, updated 17 July 2025, says a lot developed under these provisions cannot be subdivided. Don’t model a separate sale of that granny flat as the loan’s repayment exit.

A separately titled residence needs assessment as its own property. If the client means movable accommodation when they say granny flat, establish that before selecting residential construction finance. Use the tiny home finance guide for movable dwellings and land-tenure questions.

Check Title and Approvals

Check that the title and approved works describe the property the lender will take as security. Obtain the title search and site plan, then identify easements, covenants and any restrictions affecting the proposed location. Include access for construction, permanent occupant access and proposed water, sewerage and power connections.

Get the responsible council, planning authority or certifier to identify the approval pathway for this address and intended use. Supply the actual plans and title details, because an approval for a neighbouring property doesn’t establish what this site permits. Record any approval conditions that change the building cost or occupation date.

The New South Wales guidance updated 17 July 2025 allows secondary dwellings through consent or complying development when the relevant requirements are met. A proposal that fails complying-development requirements can still be assessed through a council development application. That distinction doesn’t establish the rules for another state or territory.

Separate permission to build from permission to occupy or rent. Put the required planning consent, building approval and completion or occupation evidence in the file at the stage each is needed. If the approval only permits a different use from the client’s rental plan, revise the plan before including rent in the application.

For a newly purchased site, match the purchase contract and proposed dwelling to the same title. Show who will own it at settlement and whether the main home is part of the same building project. A purchase approval alone doesn’t approve the additional dwelling or its funding.

Assess the Build Contract

Review the complete granny-flat contract against the approved plans and the funding schedule. Record the builder’s identity and licence, contract type, specifications, total price, deposit, progress claims and completion timing. Identify exclusions, provisional allowances and variations that can increase the amount the client must fund.

A fixed-price contract still needs a separate allowance for excluded works. Check whether the price includes foundations, delivery, installation, service connections, access works and completion certification. Put each excluded item beside its quote, payment date and funding source.

As at October 2026, Westpac’s residential construction guide requires a signed, dated building contract with stages and payment schedules. It also lists plans, specifications and applicable variations or quotes. These are Westpac’s general construction requirements, so the lender still needs to accept the proposed secondary dwelling and security.

Flag owner-managed construction before using a licensed-builder route. Westpac’s guide has a separate owner-builder process with independent costing advice and inspections at each stage. An owner-builder permit doesn’t by itself establish the lender’s willingness to fund this project.

For a prefabricated granny flat, compare the supplier’s deposit and factory-payment dates with the lender’s permitted release dates. A demand for payment before delivery creates a funding gap if the approved facility releases money only after installation or inspected works. Resolve that gap through an accepted payment schedule or evidenced client funds before the client commits.

Test Value and Rental Assumptions

Assess build cost, completed property value and proposed rent separately. The contract tells you what the client must pay. The lender’s valuation assesses the whole property with the completed secondary dwelling, including its marketability and approved use.

CommBank’s granny-flat guide, published 18 May 2024, explains that home equity can fund construction subject to lending criteria. It also warns that the added property value can be lower than the build cost. Keep this distinction when assessing a home equity loan for a granny flat.

This hypothetical example shows the valuation effect. Assume an existing mortgage of $500,000, a $180,000 total project cost and an $800,000 completed valuation. If the selected route’s confirmed loan-to-value ratio (LVR) limit is 80%, total secured debt can reach $640,000.

That leaves $140,000 for the project after the existing mortgage, requiring a $40,000 client contribution before any additional finance costs. If the completed valuation is $750,000, the same assumed limit allows $600,000 total debt. Available project funding falls to $100,000 and the contribution rises to $80,000.

The 80% limit is an example assumption, not a market-wide granny-flat rule. Repayment capacity can reduce the available loan further. Don’t add the full build cost to today’s value and treat the result as the completed valuation.

Use proposed rent only where the selected lender accepts it for this secondary dwelling and the evidence meets that policy. Obtain the required rental appraisal or valuer’s rental assessment, identify the accepted income amount and include property expenses. Record when lawful occupation and rent can start, including any period while construction is unfinished.

Run the assessment again with no granny-flat rent. If that fails, record how much borrowing the client can support without it and whether a smaller project or greater contribution closes the gap. Expected rent doesn’t pay invoices during the build.

For lender-policy research, Bulma’s Policy Advisor quotes the wording behind each answer. You can retain that wording with the file notes when comparing how lenders treat the secondary dwelling and proposed rent. The selected lender’s assessment decides the available finance.

Prepare the Funding File

Prepare a funding file that connects the approved dwelling, total debt and every construction payment to supporting evidence. A loan for a granny flat is ready for assessment when the lender can follow the property and the money without filling gaps itself.

Collect the following evidence for the chosen route.

• Title search, site plan and any purchase contract, including restrictions affecting the works.
• Planning and building approvals, conditions, approved plans and specifications.
• Builder details, signed contract, variations, excluded-work quotes and payment schedule.
• Required construction insurance and the existing home’s insurance details.
• Lender-ordered valuation covering the proposed works and accepted rental evidence if rent is included.
• Client funds, existing mortgage balance, refinance costs and a reconciled total project budget.
• Verified income, expenses and liabilities, with servicing results showing accepted rent and the no-rent fallback.

As at October 2026, Westpac’s renovation page lists granny flats as major renovations. It describes equity-funded borrowing and a construction option for larger or complex works. Equity is a source of security capacity, while the construction option controls how approved funds are released.

Follow this sequence to settle the funding arrangement.

1. Establish the existing mortgage treatment. Record whether it stays with the current lender or is refinanced, the required payout and the resulting total secured debt.
2. Confirm the accepted route. Obtain the lender’s terms for this secondary dwelling, build method and use, including the valuation basis and rental treatment.
3. Match payments to available funds. Put each contract claim beside the client’s contribution, permitted loan release and required inspection or document.
4. Clear conditions before work relies on the loan. Record the lender’s written authority to commence and the evidence required for the first payment.
5. Verify the completed file. Reconcile the loan offer, valuation, contract and payment schedule with the budget and servicing assessment.

Westpac’s construction guide, as at October 2026, requires the agreed borrower contribution before its progress payments to the builder. Its commencement letter sets the payment process, and required inspections must certify the works before release. For the general staged-build procedure, use the construction loan requirements guide.

If a factory claim arrives before an eligible loan draw, revisit the supplier schedule and identify the cash that covers it. If a variation exceeds the budget, update the cost to complete and funding evidence before authorising that payment. If proposed rent is excluded, use the no-rent servicing result to revise the borrowing amount.

Before the client relies on the finance, every payment must have an evidenced funding source and every loan condition must have a responsible person. Confirm that the file uses the accepted property value and rental treatment, with enough funds to complete the approved secondary dwelling.