*This estimate is for guidance only and may vary depending on lender criteria, stage payments, and interest rate fluctuations specific to Irish self-build mortgages.*
Building your own home in Ireland is an exciting journey — but figuring out the mortgage costs and repayments can be tricky.
Our Self Build Mortgage Calculator Ireland helps you estimate your monthly repayments, total interest, and loan amount in just a few seconds.
Whether you’re planning your first self-build or extending your existing property, this tool is designed to give you a clear picture of your potential mortgage costs before approaching lenders. For more property and housing tools, visit our 👉 Mortgage & Property Calculators section
🔍 What Is a Self Build Mortgage?
A self build mortgage is a special type of home loan that allows you to borrow money in stages as your home construction progresses — unlike a standard mortgage that releases funds all at once.
This type of mortgage is ideal for people who want to build their dream home on their own land or manage the construction process themselves.
In Ireland, most lenders provide funds in four to six stage payments, aligned with construction milestones — such as foundations, wall plate, roof completion, and final finish.
During the build, you might only pay interest on the amount drawn down, which keeps costs manageable while construction continues.
You can also go through - Hsscu Loan Calculator Ireland
🧮 How to Use the Self Build Mortgage Calculator
Using this calculator is simple and fast — you don’t need any technical or financial knowledge. Just follow these steps:
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Enter Your Estimated Build Cost (€) – the total amount you expect to spend building your home.
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Enter Your Deposit / Own Funds (€) – the money you already have saved for the project.
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Add the Interest Rate (% per annum) – input the mortgage rate offered by your lender (e.g., 4.5%).
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Select the Mortgage Term (years) – typically between 20 to 30 years.
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Click on “Calculate” – your estimated monthly repayments, total interest, and total repayment will appear instantly.
💡 Tip: Adjust the interest rate or term to compare different scenarios and find the most affordable repayment option for your self build.
⚙️ How the Calculator Works
The Self Build Mortgage Calculator uses the standard mortgage repayment formula (also known as the annuity formula) to calculate your monthly instalment.
Here’s what happens behind the scenes:
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It first calculates your loan amount (Build Cost − Deposit).
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Then it applies your interest rate and term to determine the monthly repayment using the formula:
where
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M = monthly repayment
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P = principal loan amount
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r = monthly interest rate
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n = number of payments (months)
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It also computes your total repayment and total interest over the full term.
This gives you a realistic picture of how much your self build mortgage will cost from start to finish.
💡 Why Use Our Self Build Mortgage Calculator Ireland?
Our calculator is designed specifically for Irish home builders and borrowers, offering tailored results for the Irish lending environment.
✅ Ireland-specific mortgage logic – matches local interest rates, loan terms, and lending conditions.
✅ Fast and accurate results – instantly shows your repayments and interest breakdown.
✅ Helps with budgeting – plan your build costs and finances before applying for a mortgage.
✅ User-friendly design – no complicated forms, just clear and easy-to-read results.
✅ Free and secure – no signup or data storage; use it anytime.
Whether you’re a first-time self builder, an architect helping clients, or a financial advisor comparing costs, this calculator gives you instant clarity on mortgage affordability.
💬 Frequently Asked Questions (FAQ)
1. What is a self build mortgage in Ireland?
A self build mortgage is a loan that releases funds in stages during construction instead of a single lump sum. You draw money as your build progresses and typically pay only interest during construction.
2. Can I use this calculator for stage payment mortgages?
Yes. This tool estimates the overall repayment once the full loan is drawn down. For detailed stage-by-stage drawdown interest, you can use our upcoming Stage Payment Self Build Calculator.
3. What deposit do I need for a self build mortgage in Ireland?
Most Irish lenders require 10–20% of the total build cost as a deposit or own funds. The calculator allows you to enter this figure to estimate your loan amount.
4. Does the calculator include legal fees or building insurance?
No, this calculator focuses on loan repayments and interest. You should budget separately for professional fees, insurance, site costs, and contingency.
5. How accurate are the results?
The results are based on standard mortgage formulas and are for estimation purposes only. Actual rates and repayments may vary depending on your lender, credit profile, and build progress.