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Granny Flat Construction Loan Calculator

Why Use Lime Mortgage Brokers' Granny Flat Construction Loan Calculator

  • Model Your Construction Loan: Understand how your construction loan may work from the first drawdown through to project completion. Our calculator estimates interest-only repayments during construction before the loan transitions to principal and interest repayments once the granny flat is complete.

  • Understand Progress Payments: Construction loans are funded in stages rather than as a lump sum. Allocate your loan across the slab, frame, lock-up, fixing/fit-out, and completion stages to see how funds may be released throughout your build.

  • Plan Your Budget with Confidence: Enter your property value, existing mortgage balance, build contract price, deposit, interest rates, and loan term to estimate your construction loan and better prepare for the financial commitment of your granny flat project.

  • Adjust Different Loan Scenarios: Experiment with different deposits, interest rates, Loan-to-Value Ratios (LVR), loan terms, and progress payment amounts to understand how changes may affect your estimated repayments during and after construction.

  • Expert Guidance: Need help understanding your results? Our experienced mortgage brokers can explain your estimates, answer your questions, and help you explore construction loan options that suit your granny flat project.

How It Works:

  1. Enter Your Property & Loan Details: Input your land or property value, existing mortgage balance, build contract price, deposit, interest rates, loan term, and maximum LVR.
  2. Allocate Your Progress Payments: Divide your construction costs across each building stage, including the slab/base, frame, lock-up, fixing/fit-out, and completion stages.
  3. Calculate Your Construction Loan: Instantly estimate your interest-only repayments during construction and your principal and interest repayments after the build is completed..
  4. Review Your Results: Use your estimates to better understand your construction loan structure and prepare for each stage of your granny flat project.
  5. Consult with an Expert: Speak with one of our mortgage brokers to discuss your results, verify your borrowing options, and receive personalised guidance before applying for construction finance.

Ready to Finance Your Granny Flat Build?

Take the guesswork out of construction finance with Lime Mortgage Brokers’ Construction Loan Finance Calculator. Model your construction loan, understand how progress payments work, and estimate your repayments throughout every stage of your granny flat build. When you’re ready, our experienced mortgage brokers are here to help you find the right construction finance solution for your goals.

Mortgage Broker Tool
Construction Loan Finance Calculator
for Granny Flat

Model the interest-only drawdown phase and ongoing P&I repayments for a construction loan to build a granny flat on your existing property.

Construction Loan Details

Set your land value, construction cost, progress payments and rates

How construction loans work: Funds are released in progress payments as each stage of the build is completed. During construction you pay interest only on the drawn balance. Once complete, the loan converts to a standard principal & interest mortgage.
$
$
$
$
6.50%
6.25%
30 yrs
80%

Progress Payment Stages

Adjust the amount drawn at each construction stage. The total must equal the loan amount (contract price minus deposit).

Stage Draw Amount % of Loan
1Slab / Base
$
—
2Frame
$
—
3Lock-up
$
—
4Fixing / Fit-out
$
—
5Completion
$
—
Important: This calculator is for illustrative purposes only and does not constitute financial advice. Construction interest costs assume each stage draws the stated amount and is held for the estimated duration before the next drawdown. Actual durations, drawdown timing, and interest calculations will vary based on your lender and builder. The post-construction P&I repayment and amortisation schedule are calculated on the combined total debt (existing mortgage balance plus the construction loan amount), assuming both are consolidated onto the P&I rate and term entered above. Always engage a licensed mortgage broker for full borrowing capacity and loan structuring advice.

Apply for the finance that you need

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