Use our self-build mortgage calculator to work out what you could borrow, the deposit you need, how the money lands in stages and what your build will actually cost to finance. It takes about a minute and you do not have to give us anything to see the result.
Self-build funding works nothing like a normal mortgage. The money comes out in stages, the lender caps you on project cost rather than the finished value, and the interest only runs on what you have drawn. The calculator is built around all three.
Your project
Enter your figures. Change one at a time and watch the result move.
We email the PDF to you. Your results stay on screen.
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We will email you a link to your PDF, and one of our self-build specialists will take a look at your figures.
We will only use these details to send you your figures and to talk to you about funding your build. Clever Lending is authorised and regulated by the Financial Conduct Authority.
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How the £0 of borrowing is likely to be released. Release points and percentages vary by lender and build method.
For illustration only. Figures are estimates based on the inputs above and do not constitute a quote, an offer of finance or financial advice. Lender criteria, valuations and final costs will differ. Clever Lending is authorised and regulated by the Financial Conduct Authority (FRN 795789).
With a standard residential mortgage the lender releases everything on completion day against a house that already exists. On a self-build there is no house yet, so the money is released in stages as the build progresses.
Most self-build lending runs on an interest-only basis while the build is live, with interest charged only on what you have drawn. When the house is finished, signed off by building control and covered by a ten-year structural warranty, the facility is repaid. Usually that means remortgaging onto an ordinary residential mortgage at the finished value, which is where most of the gain in a self-build sits.
That exit is the first thing a lender will ask about, and it needs to be credible before they lend a penny.
Stage payments are released either in arrears, after each stage is finished and inspected, or in advance, at the start of each stage. Arrears is cheaper and needs you to fund each stage first. Advance costs a little more and removes the cash flow pressure, which for a lot of self-builders is the difference between the project being possible and not.
Release points and percentages vary by lender and by build method, but a traditional brick and block project typically looks like this.
Plot purchase
20 to 25% of the facility. Often the largest single drawdown.
Foundations and damp course
10 to 15%. Inspected before release on an arrears basis.
Wall plate level
15 to 20%. Walls up, ready for the roof.
Roof watertight
15 to 20%. The point most lenders treat as the halfway mark.
First fix and plastering
15 to 20%. Wiring, plumbing and plastering.
Completion and sign-off
10 to 15%. Released on building control certificate and warranty.
Timber frame and SIPs builds shift the money forward, because a large payment falls due to the frame manufacturer early on. If you are building that way, an advance product is usually worth the extra cost.
Two limits apply at once and the lower one wins: the project cap, and your affordability.
| What lenders cap | Typical position | Notes |
|---|---|---|
| Loan to total project cost (LTC) | 75 to 80% | Plot plus build. A few lenders go higher, some sit lower |
| Loan to end value (LTGDV) | Usually 55 to 65% | Falls out of the LTC cap rather than being set separately |
| Deposit or contribution | 20 to 25% | Of project cost, plus fees and contingency on top |
| Exit mortgage | Assessed on income | Affordability on the residential mortgage that replaces the facility |
A worked example. On a £150,000 plot with a £220,000 build, total project cost is £370,000. At 80 per cent of cost that is around £296,000 of borrowing and £74,000 of contribution. If the finished house is worth £520,000, that borrowing is only about 57 per cent of end value, which is why the remortgage at the end usually goes through comfortably.
Affordability is the part people miss when they search for a self-build mortgage calculator based on salary. Even where the project stacks up, the lender still has to be satisfied you can service the debt during the build and afterwards, including the cost of running your current home at the same time. If your income is complex, from a limited company, self-employment or multiple sources, that is where cases are usually won or lost, and we arrange complex income mortgages regularly.
Build cost is the number most people get wrong, and it drives everything else in the calculator. Costs depend heavily on how much of the project you manage yourself. The figures below are UK averages for 2026.
Remote sites add materially to groundworks, often 15 to 30 per cent on the foundations alone. A 180m² house on a self-managed basis therefore lands somewhere around £290,000 to £400,000 of build cost before the plot.
| Build route | Cost per m² | What it means |
|---|---|---|
| DIY | £1,000 to £1,600 | You project manage and do a significant amount of the work |
| Self-managed | £1,600 to £2,200 | You project manage, trades do the work |
| Main contractor | £2,000 to £2,800 | A builder delivers the whole thing |
| Design and build | £2,300 to £3,500 | Single firm handles design and construction |
These are the lines that quietly turn a workable budget into a tight one. Every one of them is real, and every one of them has to come from somewhere.
| Cost | Typical | Why it matters |
|---|---|---|
| Stamp duty on the plot | Varies | Payable on the land purchase, so check the current rates before you budget |
| Structural warranty | £3,000 upwards | Required by almost every lender, and by the exit remortgage |
| Service connections | Four to five figures | Water, power, drainage and broadband to a bare plot |
| Professional fees | 8 to 12% of build | Architect, structural engineer, planning consultant |
| Stage inspection fees | Per visit | Charged each time the lender's valuer attends |
| Arrangement fee | 1 to 1.5% of loan | Usually added to the facility |
| Contingency | 10 to 15% of build | Not optional. Every finished self-build has used some of it |
| VAT | Reclaimed later | Paid as you go, refunded after completion. A cash flow gap, not a saving |
It takes about a minute. Here is what each field means and where the number should come from.
Plot or land cost
What you are paying, or what the plot is worth today if you already own it.
Total build cost
Everything from bare plot to finished house, including professional fees.
Expected value when finished
A local agent’s view, not the figure you are hoping for.
Cash available
What you can genuinely put in, including equity in the plot.
Stage payment type
Arrears if you have reserves, advance if your cash is tied up in the land.
Build term
Your builder’s programme plus a buffer for weather and building control.
Interest rate
A sensible working figure if you do not have a quote yet.
Advanced costs
The fees, warranty, stamp duty and contingency. Add them, then change one input at a time.
Open the advanced panel and add the fees, warranty, stamp duty and contingency. Those are the numbers that quietly turn a workable budget into a tight one. Change one input at a time and watch what moves.
The plot needs detailed planning permission. Outline consent is rarely enough, and any pre-commencement conditions need to be dischargeable. If access, drainage or a covenant is unresolved, sort it before you apply.
The plan needs to be credible: a costed schedule of works, a realistic programme, named and vetted contractors, and a proper contingency. Lenders are not looking for perfection, they are looking for someone who has done their homework.
Experience helps but is not essential, and first-time self-builders are funded every year. What makes the difference is how the case is presented. We know which lenders take which builds, who works on an advance basis and who will look at non-standard construction, which is usually the difference between a yes and a pass.
We are a specialist property finance brokerage, authorised and regulated by the Financial Conduct Authority. Construction-led lending is what we do daily, from single self-builds and conversions through to full development finance schemes.
Send us the outline of your project and we will come back within 24 business hours with a clear route forward and a realistic timeline. There are no fees payable until we have found you a solution.
We work with lenders that are not available to every broker, including several who take a more flexible view on advance stage payments and complex income. You get your own adviser and case manager from day one.
If you need to move faster than a self-build facility allows, for example to secure a plot at auction, bridging finance is often the better first move. If you are building to sell rather than to live in, try our buy to sell mortgage calculator, or browse all our calculators and resources.
Speak to a specialist today. Get a tailored quote or call us on 0800 316 2224. We respond within 24 business hours, and there are no fees payable until we have found you a solution.
Most lenders cap total lending at 75 to 80 per cent of your total project cost, plot plus build. You then have to pass affordability on the borrowing itself and on the residential mortgage that replaces it. The calculator covers the project side, and a short conversation covers the rest.
Usually 20 to 25 per cent of the total project cost, plus fees and contingency on top. Advance stage payment products generally need a slightly larger contribution up front than arrears products.
In most cases yes, and it is one of the strongest positions to be in. Lenders will normally count the equity in a plot you own outright towards your contribution. The plot is valued as part of the application, so what counts is its value now with planning in place, not what you paid.
The loan is released at agreed milestones rather than in one lump, typically plot, foundations, wall plate, roof watertight, first fix and completion. Arrears releases follow each completed and inspected stage. Advance releases arrive at the start of the stage. Interest normally runs only on what you have drawn.
Yes, though the pool of lenders is smaller and they will look harder at your plan. A costed schedule of works, a vetted contractor, a realistic programme and a proper contingency matter more than experience.
They sit above standard residential rates because the lender carries construction risk on a property that does not exist yet. Pricing moves with loan to cost, build type, your experience and whether you want advance or arrears drawdowns. Rates change month to month, so we quote live pricing for your project rather than a figure that dates.
Most self-build lending is interest-only during the build, which keeps outgoings down while you may also be running your current home. Some lenders roll the interest up so you pay nothing monthly and settle at the end. Repayment normally starts on the residential mortgage that follows.
It is a specialist corner of the market: building societies, a handful of banks and some dedicated self-build funders. They differ enormously on maximum loan to cost, advance versus arrears, first-time self-builders and non-standard construction. That variation is why going direct to one lender is a gamble.
In most cases yes. Labour on a new build should be zero rated and you can usually reclaim VAT on materials through HMRC’s DIY housebuilders scheme. You pay it as you go and claim it back within six months of completion, so budget it as a cash flow gap. Keep every invoice.
Yes, but it usually needs the right lender rather than the biggest one. Some want two or three years of accounts, others will work from one year or from retained profit rather than drawings. Worth a conversation before you commit to a plot.
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