Common Mistakes When Funding an Extension Project

A construction loan for an extension works differently to standard home loan finance.

Most Adelaide homeowners assume they can treat an extension the same way they would a renovation, drawing the full amount upfront and managing payments to the builder themselves. That assumption creates funding gaps, particularly when council approval runs longer than expected or when the builder's progress payment schedule doesn't align with how the lender releases funds.

Why Extension Projects Require Construction Finance

Lenders release funds progressively as the build reaches defined stages, not as a lump sum at settlement. This applies whether you're adding a second storey in Norwood or extending a character cottage in Unley. The loan is structured around a progress payment schedule tied to inspections, which means the builder receives payment only after each stage is verified and approved by the lender's valuer.

You only pay interest on the amount drawn down at each stage, not the full approved loan amount. During the construction phase, most lenders offer interest-only repayment options, which keeps your outgoings lower while the work is underway. Once the extension is complete and you receive the Certificate of Occupancy, the loan converts to a standard home loan with principal and interest repayments.

Fixed Price Contracts and Why They Matter to Lenders

Most lenders will only approve construction finance when you have a fixed price building contract with a registered builder. The contract needs to include a detailed progress payment schedule that shows exactly how much will be paid at each stage, from base stage through to practical completion.

Consider a homeowner in Prospect adding a rear extension and updating the kitchen. The builder quotes $180,000 on a cost plus contract, which allows for variations as the project unfolds. The lender declines the application because the final cost isn't locked in. The homeowner returns to the builder, negotiates a fixed price contract at $185,000 with a clear schedule, and the application is approved within two weeks. The slightly higher contract price was offset by certainty, and the lender could assess serviceability based on a known loan amount.

Without a fixed price contract, the lender can't determine whether you can afford the completed project or whether the security value will support the debt. A cost plus contract might suit some builders, but it rarely suits a lender's credit policy.

When the Extension Starts Before You Settle

Some buyers purchase a home specifically to extend it, and the builder is ready to start before settlement occurs. This creates a timing issue. Construction loans are typically structured so that the first drawdown happens at settlement, but if the builder has already commenced work or ordered materials, you'll need to address that upfront.

You can't draw construction funds before you own the property. If the builder needs a deposit or progress payment prior to settlement, you'll need to fund that separately, either from savings or a personal loan. Once settlement completes, the construction loan activates and the remaining progress payments proceed as scheduled.

Some lenders allow you to include pre-settlement costs in the total loan amount, provided you can demonstrate those costs with invoices and a signed contract. Others will not. If you're in this situation, raise it with your broker during the application stage, not two days before settlement.

The Progressive Drawing Fee and How It Adds Up

Every time the lender releases funds to the builder, they charge a Progressive Drawing Fee to cover the cost of the valuer's inspection. This fee typically ranges from $150 to $400 per drawdown, depending on the lender and the location of the property.

If your builder's progress payment schedule includes six stages, you'll pay that fee six times. On a $200,000 extension with a typical five-stage schedule, you might pay $1,500 to $2,000 in drawing fees over the course of the project. These fees are separate from your loan and are usually debited from your nominated account at each drawdown.

Some lenders cap the number of drawdowns or allow you to consolidate stages to reduce fees. Others don't. The fee structure should be confirmed before you sign the loan documents, particularly if your builder has structured the contract with more frequent payments than the lender typically accommodates.

Council Approval and What Happens When It Delays

Construction finance approvals are often conditional on receiving council approval and a building permit before settlement or before the first drawdown. If your development application is still being assessed, the lender will issue conditional approval but won't release funds until that approval is finalised.

In Adelaide's inner suburbs, where character overlays and heritage considerations apply, council approval can take longer than anticipated. A homeowner in Norwood Park submitted plans for a rear extension in line with the council's development plan, but the application required a second round of consultation due to overlooking concerns from a neighbour. The delay pushed settlement back by six weeks, and the builder's start date had to be renegotiated. The loan remained approved, but no funds were released until the council plans were stamped.

If you're relying on settlement to fund the deposit to the builder, a delay in council approval will delay everything downstream. Build that buffer into your timeline, particularly if the project involves a second storey, a boundary wall, or any element that might attract neighbour objections.

How Serviceability Is Assessed for Extension Finance

Lenders assess your ability to service the loan based on the total amount you'll owe once the extension is complete, not just the amount you currently owe on the property. If you're borrowing an additional $200,000 to fund the extension, the lender will test your income against the full debt, even though you're only paying interest on drawn amounts during construction.

This is where some applications fail. A borrower might comfortably afford the interest-only payments during the build but can't demonstrate they'll manage the principal and interest repayments once the loan converts. If you're close to your borrowing capacity, an extension project might push you over the line unless your income has increased or your other debts have reduced since you first purchased the property.

Owner Builder Finance and Why It's Harder to Secure

If you're planning to manage the extension yourself as an owner builder, most mainstream lenders will decline the application outright. Owner builder finance is available, but it's offered by a smaller panel of lenders, usually at a higher interest rate and with more stringent drawdown conditions.

The lender's concern is that an owner builder project has a higher risk of cost blowouts, delays, and incomplete work. Without a registered builder and a fixed price contract, the lender has no third party to hold accountable if the project stalls. If you're set on managing the build yourself, you'll need to work with a broker who has access to specialist construction lenders and be prepared for a larger deposit requirement, often 20% or more.

What Happens If the Build Runs Over Budget

Once your construction loan is approved and the contract is signed, the loan amount is fixed. If the project runs over budget due to variations, unforeseen structural issues, or material cost increases, the lender won't automatically increase your loan.

You'll need to either cover the additional cost from your own funds or apply for a loan top-up, which requires a new assessment of your serviceability and the property's value. Some lenders allow a small contingency buffer to be included in the original loan amount, but that needs to be factored in at application stage.

If you're extending an older home in a suburb like Goodwood or Hyde Park, where you're more likely to encounter unexpected issues once walls are opened up, speak with your builder about including a contingency allowance in the contract and your broker about whether that can be reflected in the loan structure.

Moving from Interest-Only to Principal and Interest

Once the extension is complete and you've received the Certificate of Occupancy, the loan converts from construction mode to a standard home loan. Your repayments shift from interest-only on the drawn amount to principal and interest on the full loan balance.

That shift can be significant. During a six-month build, you might have been paying $1,200 per month in interest-only payments. Once the loan converts, that could increase to $2,400 per month depending on the loan amount and interest rate at the time. If your financial position has changed during the build, or if rates have moved, that repayment might be higher than you planned for.

Some lenders allow you to lock in a portion of the loan at a fixed rate once the construction is complete, which can provide certainty if you're concerned about rate movement. Others offer the option to extend the interest-only period for a further 12 months, though that depends on your equity position and the lender's policy at the time.

Call one of our team or book an appointment at a time that works for you. We'll review your project, confirm which lenders will support the structure you need, and make sure the progress payment schedule aligns with how the funds will actually be released.

Frequently Asked Questions