Avoid These 5 Mistakes with Extension Construction Loans

When Standard Home Loans Don't Cover Your Extension

A standard home loan won't release funds progressively as your extension gets built. Construction loans differ because they only charge interest on the amount drawn down at each stage, releasing money as your builder completes specific milestones rather than handing over the full loan amount upfront.

In Carnegie, where many period homes sit on generous blocks, extending rather than moving has become a common choice. The local council receives development applications regularly for rear extensions, second-storey additions, and garage conversions. Financing these projects requires a loan structure that aligns with how builders get paid.

How Progressive Drawdowns Match Your Builder's Payment Schedule

Your builder doesn't wait until the extension is finished to get paid. They invoice at set stages based on completed work, and your lender releases funds to match those invoices. Most lenders work with a standard five-stage drawdown: base stage, frame stage, lockup stage, fixing stage, and completion.

Consider a homeowner adding a two-bedroom extension to a Victorian cottage near Koornang Road. The builder's fixed price contract breaks the project into progress payments. At the base stage, once the slab is poured and inspected, the lender releases the first drawdown. The builder uses that to pay sub-contractors and order materials for framing. At frame stage, once the timber frame is up and the roof is on, the next payment releases. This continues through to completion.

The lender charges a Progressive Drawing Fee each time they release funds, typically between $300 and $500 per drawdown depending on the lender. Some lenders cap this at a total fee across all stages. You'll also need a quantity surveyor or independent inspector to confirm each stage is complete before the lender releases payment. That inspection fee sits separate from the lender's fee and usually costs between $150 and $250 per visit.

Fixed Price Contracts Versus Cost Plus Contracts

Most lenders will only approve construction finance if you have a fixed price building contract with a registered builder. The contract needs to show the total project cost, the progress payment schedule, and a start date. Lenders assess your borrowing capacity based on that fixed price, so they know exactly how much the project will cost and whether you can service the loan.

A cost plus contract, where the builder charges for actual costs plus a margin, creates uncertainty. Lenders can't determine the final loan amount, and most won't proceed without a fixed price. If you're using an owner builder arrangement, where you're managing sub-contractors yourself, fewer lenders will consider the application, and those that do typically require larger deposits and charge higher interest rates.

In Carnegie, where many homes are heritage listed or require planning permits through Stonnington Council, your construction loan application will also need council approval before a lender will proceed. The lender wants to see that your development application has been approved and that you can commence building within a set period from the disclosure date. If council approval is still pending, most lenders will issue conditional approval but won't release any funds until you provide the stamped plans.

Why Lenders Want to See Your Existing Equity

Lenders assess construction loans differently than purchase loans. They want to see that you have enough equity in your existing property to cover the cost of the extension, or enough savings to top up the difference. If your home is worth $1,100,000 and you owe $400,000, you have $700,000 in equity. If your extension costs $250,000, the lender will typically allow you to borrow up to 80% of the combined value, meaning the value of your home plus the extension once complete.

The challenge comes when the valuer assesses what your home will be worth after the extension is built. They provide an 'as if complete' valuation, estimating the future value based on your plans and the local market. If that valuation comes in lower than expected, you may need to contribute more from savings to make up the gap. This happens more often in areas where the cost of building has increased faster than property values.

For a home improvement loan in Carnegie, where the median house price sits around $1,500,000, adding a $200,000 extension doesn't always increase the property value by the same amount. The valuer considers comparable sales, and if similar homes with extensions haven't sold recently, they may take a conservative view. That's why having a buffer in your budget matters.

Interest-Only Repayment Options During Construction

During the construction period, most lenders offer interest-only repayment options. You're only charged interest on the amount drawn down so far, not the full loan amount. Once the extension is complete and the final drawdown is made, the loan typically converts to a standard principal and interest home loan, and you start repaying both the interest and the loan amount.

Some lenders allow you to continue on interest-only repayments for a set period after construction finishes, usually up to five years. This can help if your budget is tight immediately after the build, but you'll pay more interest over the life of the loan if you delay paying down the principal.

If you're refinancing your existing home loan at the same time to fund the extension, you can often negotiate a lower construction loan interest rate by consolidating both loans with the same lender. However, if your current home loan has a competitive rate and you're still within a fixed rate period, breaking that loan early may trigger break costs that outweigh any benefit from refinancing. In that case, keeping your existing loan and adding a separate construction facility can be more cost-effective. A mortgage broker in Carnegie can compare both structures and calculate which approach saves more over the full loan term.

Avoiding the Top Five Mistakes with Extension Finance

The first mistake is underestimating the timeline. Construction loans require more documentation than standard home loans. You'll need council-approved plans, a fixed price building contract, a soil test, engineering reports if required, and builder insurance. Gathering these documents takes time, and lenders won't proceed without them. Start the loan application before your builder is ready to start, not after.

The second mistake is assuming your current lender will automatically approve the construction loan. Even if you have an existing home loan with them, they'll reassess your income, expenses, and the property's value. If your financial situation has changed or the valuation comes in low, they may decline or offer less than you need. Applying with multiple lenders through a broker gives you options if your current lender won't proceed.

The third mistake is not budgeting for the Progressive Drawing Fee and inspection costs. If your project has five drawdowns and each costs $400 in lender fees plus $200 for inspections, that's $3,000 in fees before you've paid a single tradesperson. Factor these into your total project budget.

The fourth mistake is choosing a builder who isn't registered or doesn't have adequate insurance. Lenders require evidence that your builder holds current registration and appropriate levels of cover. If your builder can't provide this, the lender won't approve the loan.

The fifth mistake is not allowing a contingency in your budget. Building costs can increase if you uncover structural issues, asbestos, or poor drainage once work begins. A contingency of 10% to 15% of the total project cost gives you room to cover unexpected expenses without scrambling to find additional funds mid-project.

Converting to a Standard Home Loan After Completion

Once your extension is finished and the final inspection is done, the lender converts your construction facility to a standard home loan. At this point, you'll move from interest-only repayments to principal and interest, unless you've arranged to stay on interest-only for a set period.

This is also the point where you can refinance if you want to access a lower rate with a different lender. Some borrowers use the construction phase to lock in the funding, then refinance once the extension is complete and the property has been revalued at its new, higher value. That higher valuation can improve your loan-to-value ratio and give you access to better rates.

If you're planning to use your extended home as an investment property after completion, switching to an investment loan structure at this point may offer tax benefits, as the interest becomes deductible. Speak to your accountant before making this change, as the timing and structure affect how much you can claim.

Construction finance for an extension involves more moving parts than a standard home loan, but it's designed to match how building projects actually work. Starting with a clear fixed price contract, allowing time for council approvals, and budgeting for the full cost including fees and contingencies will set your project up to run without funding delays. Call one of our team or book an appointment at a time that works for you to discuss your extension plans and work out the loan structure that fits your budget and timeline.

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