Understanding the Basics of Extension Financing

Extension projects use construction finance structured around progressive drawdowns rather than a single lump sum.

You're not building from scratch, but you're not doing a cosmetic renovation either. Adding a second storey, extending out the back, or building a granny flat requires construction finance because the work happens in stages and the money needs to follow the progress. Most lenders treat extensions the same way they treat new builds, which means you'll deal with progress payments, building inspections, and drawdown schedules instead of just getting the full loan amount upfront.

How Construction Finance Works for Extensions

You only pay interest on the amount drawn down so far, not the full loan amount. The lender holds the total approved sum and releases it in stages as your builder completes specific milestones like slab pour, frame lock-up, fixing stage, and practical completion. Each release requires a progress inspection to confirm the work matches what's been invoiced. Between drawdowns, you're charged interest on whatever's been released, which keeps your repayments lower during the build phase compared to paying interest on the entire loan from day one.

Consider an officer extending their home to add a fourth bedroom and second living area. The total build cost sits at $180,000 across five progress payments. After the first drawdown of $36,000 for site preparation and footings, they're paying interest on that portion only. By the time the frame is up and the second drawdown of another $54,000 comes through, interest applies to the combined $90,000. This continues until practical completion, when the full amount has been drawn and the loan converts to a standard home loan refinancing arrangement.

Fixed Price Building Contracts and Why They Matter

Lenders require a fixed price building contract before approving construction finance. This document locks in the total cost, the scope of work, and the payment schedule so the lender knows exactly what they're funding and when each drawdown will occur. Without a fixed price contract, most lenders won't proceed because cost blowouts become their risk as much as yours. The contract also protects you by holding the builder to an agreed price, which matters when you're halfway through an extension and can't afford surprise variations.

Your builder needs to be registered and the contract needs council approval before any lender will release funds. The development application and council plans form part of your loan application because they confirm the project is legitimate and complies with local regulations. Lenders also check that the builder holds appropriate insurance and licensing, which removes some of the risk from funding a project that might not get finished.

Progress Payment Schedules and How Drawdowns Are Timed

The progress payment schedule in your building contract dictates when you can request each drawdown from the lender. Typical schedules split the build into four to six stages, with payments tied to completed work rather than calendar dates. You can't request the frame payment until the frame is up and signed off by an independent inspector. If your builder falls behind or if you're waiting on materials, the drawdown waits too, which can stretch out the build and the period you're paying interest on a partially drawn loan.

In our experience, officers working rotating rosters appreciate lenders that allow drawdown requests and progress inspections to be handled online or by phone rather than requiring face-to-face appointments during business hours. Some lenders charge a progressive drawing fee each time you request a release, typically between $300 and $500 per drawdown. Others bundle this into a single upfront fee. Ask about the fee structure during your construction loan application so you're not surprised when the builder requests the next payment.

Interest-Only Repayment Options During Construction

Most construction loans default to interest-only repayments while the build is underway. You're not reducing the principal because the loan amount keeps increasing with each drawdown, so the repayment structure reflects that. Once the build reaches practical completion and the loan converts to a standard mortgage, you'll switch to principal and interest repayments unless you specifically arrange otherwise. The interest-only period keeps your outgoings lower while you're also managing rates, insurance, and possibly rent or a mortgage on your current property if you've moved out during the build.

When the Loan Converts and What Happens Next

After practical completion and the final drawdown, the construction loan converts to a standard home loan. The interest rate often changes at this point because construction loan rates can sit higher than standard variable rates, though not always. The conversion happens automatically once the lender receives confirmation that the work is finished and the builder has been paid in full. You'll move from interest-only to principal and interest repayments, and your repayment amount will jump because you're now paying down the full loan amount rather than just covering interest on a partially drawn balance.

If you've used construction finance to extend a property you already have a mortgage on, you'll end up with two loans unless you refinance them into a single facility once the build is done. Some lenders let you roll the construction loan and the existing mortgage together from the start, which simplifies your repayments and often gets you a lower rate on the combined amount.

What Lenders Look for in an Extension Application

Your borrowing capacity needs to cover the combined total of your existing mortgage and the construction loan, even though you're only paying interest on the extension during the build. Lenders assess your income against the full principal and interest repayment that will apply once the loan converts, not just the interest-only amount you'll pay during construction. Shift penalties, overtime, and higher duties count as income if they're regular and documented, which works in your favour if you're in law enforcement and your payslips show consistent penalty rates.

The lender will also want a valuation that reflects the home's worth after the extension is complete, not just its current value. If you're extending a property in a suburb where similar renovated homes are selling well, the post-construction valuation supports a higher loan amount. If the extension over-capitalises the property relative to the suburb's price ceiling, the lender might reduce the approved amount or ask for a larger deposit to cover the gap.

Owner Builder Finance and Why It's Harder to Arrange

If you're planning to manage the extension yourself rather than hiring a registered builder, most mainstream lenders won't touch it. Owner builder finance exists, but it's offered by a narrower group of lenders and typically comes with higher rates and stricter conditions. The lender's risk increases when there's no licensed builder guaranteeing the work, so they compensate by charging more and requiring larger deposits. Unless you've got genuine building experience and the time to manage subcontractors around your roster, using a registered builder makes the finance side far less complicated.

Call one of our team or book an appointment at a time that works for you. We work with lenders who understand shift work and can structure drawdowns and inspections around your availability, not just standard business hours.

Frequently Asked Questions