Construction loan calculator South Africa
See what a building bond actually costs, stage by stage — the interest-only payments while your builder draws, and the full instalment once the build completes. No signup needed.
Enter your build details
These numbers are illustrative estimates, not an offer. Your actual rate, deposit requirement and drawdown schedule depend on your credit profile and each bank's assessment.
Illustrative default — banks and builders structure draws differently. Edit the shares and durations to match your build contract.
Last updated: 2026-09-12. Prime is shown as 10.5%. Your actual rate depends on your credit profile, deposit and the bank’s assessment.
| Stage | Draw | Drawn to date | Months | Monthly (interest only) |
|---|---|---|---|---|
| Foundation & slab | R 405 000 | R 405 000 | 3 | R 3 544 |
| Structure & roof | R 405 000 | R 810 000 | 4 | R 7 087 |
| Fittings & finishes | R 337 500 | R 1 147 500 | 3 | R 10 041 |
| Final completion | R 202 500 | R 1 350 000 | 2 | R 11 812 |
Your building bond would be R 1 350 000 (build cost less deposit). During the build you service interest only on what has been drawn — starting near zero and rising to R 11 812 a month once fully drawn. When the build is complete, the loan switches to a full instalment of R 13 478 over 20 years.
Estimate only — assumes interest-only payments on drawn amounts during the build, the full loan amortised over the term from completion, no fees, insurance or cost overruns. Not a quote or pre-approval.
Take the drawdown planner to your builder
Save your personalised Building-cost & drawdown planner — the stage table above plus your estimated instalment — and we'll help you turn it into a bank-ready pre-qualification.
Why drawdowns change everything
A building bond is the only home loan where the amount you owe grows as the build progresses. The bank pays your builder in stages — foundation, structure, finishes — and each payment increases the balance your interest is calculated on. So unlike an ordinary bond, there is no single “monthly repayment” during the build: your payment starts small when only the foundation is funded and steps up with every draw.
On a R1 500 000 build with a R150 000 deposit at the current prime rate of 10.50%, the interest-only payment starts at R 3 544 a month once the first stage is drawn and rises to R 11 812 when the final stage is advanced. Across the 12-month build the drawdown phase costs roughly R 92 728 in interest — and then the loan converts to a full instalment of R 13 478 over 20 years.
| Stage | Draw | Drawn to date | Months | Monthly (interest only) |
|---|---|---|---|---|
| Foundation & slab | R 405 000 | R 405 000 | 3 | R 3 544 |
| Structure & roof | R 405 000 | R 810 000 | 4 | R 7 087 |
| Fittings & finishes | R 337 500 | R 1 147 500 | 3 | R 10 041 |
| Final completion | R 202 500 | R 1 350 000 | 2 | R 11 812 |
Worked example on a R1 500 000 build with a R150 000 deposit at the illustrative default stage split, prime rate of 10.50% as of 2026-09-12. Edit every input in the calculator above to match your own build.
How the calculator works
The calculator models the two phases of a South African building bond. During the build, each stage draws its share of the loan at the start of that stage and you pay interest only — on the total drawn to date, at your entered rate — for the stage's duration. After the final stage, the full loan (build cost less deposit) amortises over your entered term using the standard annuity formula South African banks use.
The default four-stage split is an illustrative shape, not a bank's rule — builders and banks structure draws differently, so edit the shares and durations to match your actual build contract. For the repayment on a standard single-advance purchase, use the bond repayment calculator, and for what you can afford overall, the home loan affordability calculator.
Assumptions: each stage draws at the start of its window and the drawn balance is constant for that window; interest-only payments during the build; the full loan amortises over the entered term from completion; the post-completion instalment assumes the term restarts at completion, as banks typically reset it; no fees, insurance, cost overruns or interest capitalisation. Rand values are rounded to the nearest rand for display only — calculations keep full precision.
Last updated: 2026-09-12.
What to do next
- New to building loans? Read the complete guide to building loans in South Africa.
- Working out what you can borrow in total? Check affordability with the home loan calculator.
- Ready to get the banks competing over your build? Start with a bond pre-approval.
- Want a human to sense-check your stage plan? Talk to a registered bond consultant.
This calculator is for illustration only and does not constitute financial advice. The rate you are offered depends on your credit profile, deposit, and the bank's assessment. Rates are current as of 2026-09-12.
Common questions about construction loans
How do construction loan repayments work in South Africa?
A building bond is not paid out in one lump sum: the bank advances the loan to your builder in stages as certified work completes. During the build you typically service interest only — on the amount drawn to date, not the full loan — so your payment starts small and rises with each draw. Once the build is complete, the loan switches to a normal reducing-balance instalment over the agreed term. The calculator above models exactly that progression.
How is interest charged during the drawdown period?
Interest is charged monthly on the outstanding drawn balance. Each time a stage is paid out to the builder, the balance — and therefore your interest-only payment — steps up. On a R1 350 000 building bond at the current prime rate, the interest-only payment grows with each draw and reaches its peak once the final stage is advanced, before converting to the full instalment at completion.
What deposit do you need for a construction loan?
Deposit requirements vary by bank and depend on your credit profile, the build contract and whether you are buying the land at the same time — many lenders ask for a larger deposit on a building bond than on an ordinary purchase because construction carries more risk. The calculator lets you enter whatever deposit you have and see the effect on the loan amount and every stage payment. Treat it as a planning tool: the actual requirement is set by each bank’s assessment of your application.
What is the difference between a construction loan and an ordinary home loan?
The money moves differently. An ordinary home loan is advanced in one payment on registration; a building bond is advanced progressively against certified stages of work. That is why a construction loan has two repayment phases — interest-only on drawn amounts during the build, then a full instalment covering interest and capital after completion. This calculator models both phases; for a single-advance purchase, use a standard bond repayment calculator instead.
Can I change the drawdown stages in the calculator?
Yes. The four-stage default (foundation & slab, structure & roof, fittings & finishes, final completion) is an illustrative shape — banks and builders structure draws differently. Edit each stage’s share of the loan and its duration in months to match your own build contract, and the table recalculates the draw amounts and interest-only payments instantly.
Get one bank to fund your build — or let them all compete
One application goes to every major South African bank. No phone calls unless you ask.