Quick summary
A construction loan is approved for a total amount, but the money is released to your builder in stages as work is completed. Interest is commonly charged on the drawn amount, lenders usually want a written building contract, and an as-if-complete valuation sets the security. Lenders vary, so confirm the details with your provider.
How Do Construction Loans Work? You Borrow Once, the Money Moves in Steps
So, how do construction loans work in practice? A lender approves a limit against your plans and contract, then releases the money to your builder in stages as work is completed. Put simply, a construction loan explained in one line is a single approved loan drawn down in steps, with interest charged on the amount drawn so far.
A construction loan is a home loan built around a project, not a purchase. When you buy an existing home, the lender pays the seller once, at settlement. When you build, there is no finished property to hand over on day one, so the lender releases money to your builder as work is completed. The total you can borrow is approved up front, but you only receive the funds as each part of the build is done.
That single difference explains many of the rules that follow. It is why the lender wants to see your building contract, why it may send a valuer, and why the interest you pay during the build usually starts small and grows. If you are still weighing up whether to build, buy or knock down and rebuild, our construction home loans guide covers the options and the borrower types who use them.
Interest Only During Construction: On the Drawn Amount, Not the Full Limit
During the build, lenders commonly charge interest only on the amount that has actually been paid out, not on the full approved limit. Imagine you have been approved for a loan and the first stage has been paid to your builder. You are being charged on that stage's amount, not the balance still waiting to be drawn.
The result is that repayments during construction are usually lower at the start and rise as more of the loan is drawn. Many lenders offer interest-only repayments during the construction period, followed by a move to principal and interest once the build is complete, but the options, the maximum length of the interest-only period and the assessment all vary by lender. Ask your broker to explain exactly how it works for the lender they recommend.
Keep in mind you may still be paying rent, or a mortgage on your current home, while the new house goes up. Lenders assess your ability to repay the full loan, rather than the smaller interest-only amounts during the build, so build a realistic budget for the whole period. Our home loan calculators can help you test different scenarios.
Why a Fixed-Price Contract Matters to Lenders
Lenders generally want a written building contract with a clear price, a scope of works and a payment schedule before they approve a construction loan. A fixed-price contract, where the builder commits to a set price for defined work, gives the lender a clearer picture of what the finished home will cost and how much money is needed at each stage.
This is not a rule for every situation. Some lenders will consider other contract types, and owner-builder projects are assessed on a different basis, as we explain in our owner-builder loans guide. But if your builder offers a cost-plus or provisional-sum-heavy contract, expect more questions, because the total cost is less certain.
Where fixed-price contracts can still surprise you
- Provisional sums and prime cost items. These are allowances for items not yet chosen, such as tiles, fixtures or site costs. If your actual choices cost more, the contract price rises.
- Variations. Changes you request after signing are extra to the contract.
- Site conditions. Rock, poor soil or drainage issues can add cost that the original price did not cover.
If you think your project could exceed the approved amount, read our guide to construction cost overrun loans before you sign.
The “As If Complete” Valuation
When you apply, the lender needs to know what the finished home will be worth, because that value sets the security for the loan. It does this by asking a valuer to assess the property on an “as if complete” basis. The valuer looks at your land, your plans and specifications and the building contract, then estimates the value of the finished house on that land.
This has two consequences. First, the loan-to-value ratio is calculated against the as-if-complete value, so the numbers depend on the valuer's opinion, which may be different from your builder's price. Second, the valuer will usually return during or at the end of the build to confirm that the work matches the plans. Some lenders inspect at set stages, others at the end, and the fees for those inspections vary, so ask what they will cost.
If you already own the land, its value and any loan on it may be taken into account in the overall structure. If you are buying the land at the same time, the lender will usually manage the land purchase as the first step and then the building stages. Your broker can explain how your own case would work.
Construction Loan Explained: How the Stages Fit Together
A typical build moves from deposit through base, frame, lock-up and fixing to completion. Each stage produces an invoice, and your lender pays the builder once its requirements are met. We break each stage down, with what triggers each draw, in our construction loan progress payments guide for NSW, so we will not repeat every step here.
What matters at the mechanics level is that the lender controls the money, but you control the sign-off. Lenders commonly ask you to sign each invoice, which confirms you accept the stage as complete. Be careful about signing early to keep a builder happy, because once funds are drawn you are borrowing them, and interest starts on that amount.
What Happens at Completion
When the build is finished and the final payment is made, the loan moves out of the construction phase. Lenders commonly ask for evidence of completion, such as a final inspection, the occupation certificate and an insurance certificate for the finished home. After that, the loan generally operates as a standard home loan under the terms you agreed, and any interest-only period during the build ends.
The point that catches some borrowers is the change in repayment type. If you were paying interest only during the build, your repayments can step up when the loan reverts to principal and interest, so plan for it. Lenders also commonly set a maximum time for the build to be completed, and the limit and the rules for extensions vary, so ask what would happen if your build ran late.
Who Uses Construction Loans, and Which Lenders Lend
People build for many reasons. Some want a new home on land they own, others are buying land and building together, and others are demolishing an existing house to start again. Our knockdown rebuild loan guide covers that last case. First home buyers should also look at the first home buyer loans page, and self-employed borrowers can read about self-employed construction loans.
Policy on deposits, contract types, income documentation and build limits varies by lender. Some borrowers are a better fit for non-bank lenders, which we cover in our guide to construction loans with non-bank lenders. Rather than guessing which lender suits your build, your broker will match you to a suitable lender based on your contract, income and situation. Because lender policy changes, confirm current requirements with your chosen provider before you apply.
Risks Worth Understanding Before You Sign
- Builder insolvency. If your builder fails during the job, work stops and you may need to finish the build with another builder. NSW has protections for residential building work, so read the NSW Government building guidance and confirm your cover before you sign.
- Delays. Weather, approvals and supply issues can extend the build. Your loan may have a time limit, and rent or holding costs continue in the meantime.
- Cost increases. A fixed price is not always the final price once variations are added.
- Valuation shortfall. If the as-if-complete value comes in below expectations, you may need a larger deposit.
The independent government consumer site ASIC MoneySmart is a good place to read general information on home loans, repayments and the risks of borrowing.
Frequently Asked Questions
How do construction loans work with interest, and do I pay on the full amount from day one?
Lenders commonly charge interest on the amount drawn so far rather than on the full approved limit, so the interest charge grows as more of the loan is paid out. The terms depend on your loan, so confirm with your provider.
What does an as-if-complete valuation mean?
It is a valuer's estimate of what your finished home will be worth, based on your land, plans, specifications and building contract. Lenders use it to set the security for the loan.
Do I need a fixed-price building contract?
Lenders generally want a clear written contract, and a fixed price gives them more certainty about the total cost. Requirements vary by lender and by project type, so ask your broker what your chosen provider will accept.
What happens to the loan when the build is finished?
After the final payment and completion evidence, the loan generally moves to the ongoing repayment arrangement in your loan terms. If you were paying interest only during construction, repayments can rise when principal and interest begins.
Can I build on land I already own?
Yes, many borrowers do, and the value of the land can be taken into account by the lender. How much it helps depends on the lender, so speak to your broker.
How long do I have to finish the build?
Construction loans commonly have a maximum construction period, and the length and the rules for extensions vary by lender. Ask before you sign the contract.
Information checked on 1 October 2026. Policies, documentation requirements and lender processes may change. Confirm the progress payment process, inspection requirements and fees directly with your chosen provider before applying. This information is general in nature and does not take your objectives, financial situation or needs into account. Policies vary by lender and change frequently — confirm current requirements with your chosen provider and seek professional advice.
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