Self Build Mortgages: the middle ground between a mortgage and a bridge
A self build mortgage releases the money in stages as your home goes up. It's assessed on your income like a normal mortgage, but it's built for a project, like development finance. Around 12,000 people build their own home in the UK every year, and most of them are quoted only one product. We quote both.
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What a self build mortgage is
Three products can fund a build, and they're not interchangeable. A normal mortgage lends against a finished house, so it can't help you mid-build. Bridging and development finance lend against the project, are priced by the month for speed, and are repaid by a sale or a refinance. A self build mortgage sits between the two: it's a long-term mortgage on the home you're creating, assessed on your income the way any mortgage is, but with the money released in stages as the build progresses.
The important difference comes at the end. With a bridge or a development loan you've to exit — sell, or refinance onto something else, and you need that exit agreed before you borrow. With a self build mortgage there's nothing to exit. When the house is finished the mortgage simply carries on as your long-term mortgage, and most lenders will let you move onto one of their standard products at that point.
It isn't only for building a new house from a bare plot. Self build lending also covers custom builds on serviced plots, barn conversions and substantial renovations, though the documents each of those needs are slightly different.
"Most people who ring about a bridging loan for a build have never heard of a self build mortgage. Sometimes the bridge is still right — speed or an unusual project usually decides it — but you should hear both quotes before you choose. Very few brokers will show you both. We will."
How the stage releases work
Most build projects are funded across six stages:
- Purchasing the land
- Initial project costs and laying foundations
- Construction to wall plate level, and the timber frame erected if there is one
- Building made wind and watertight
- First fix and plastering
- Second fix through to completion
The lender releases funds at the end of each stage, once the work has been done and checked. Read that sentence again, because it's the single thing that catches people out: the money follows the work, it doesn't fund it. You need cash, savings or an overdraft facility in place to pay for each stage before the drawdown arrives. It's the same discipline we go on about with development drawdowns, and it's why a stage-by-stage cash flow budget is the first document any decent self build lender asks for.
Some lenders will look at advance-stage releases for parts of a project, and most will discuss a funding schedule that suits an unusual build rather than forcing the standard six. That's a conversation to have before you apply, not after.
A worked example of the budget
Here is the shape of a typical new build cash flow. The figures below are the illustrative example published in one specialist lender's intermediary guide — they're not a quote, and costs vary enormously from project to project, but the structure is the thing to look at.
| Cost line | Amount |
|---|---|
| Purchase of the land | £150,000 |
| Initial costs and laying foundations | £35,000 |
| Construction to wall plate level (and timber frame) | £40,000 |
| Building made wind and watertight | £20,000 |
| First fix and plastering | £17,000 |
| Second fix to completion | £48,000 |
| Architects and project management fees | £25,000 |
| Survey, planning and associated fees | £5,000 |
| Buildings warranty insurance | £2,000 |
| Contingency, built into the costings | £33,000 |
| Total budget requirement | £375,000 |
Illustrative only, from a specialist lender's published 2023 intermediary guide. Lender criteria change — we check current terms on every case.
Two things in that table are worth pulling out. The first is the contingency: lenders generally want to see a minimum of somewhere between 5% and 10% of build cost held back, depending on the project and the contract, and they want it inside the costings rather than as a hopeful afterthought. The second is that £75,000 of the £375,000 is the self builder's own money. Lenders expect you to have skin in the game, and on most schemes they expect you to put yours in first.
How much you can borrow
Self build lending is capped from two directions at once. It has to pass affordability like any residential mortgage — your income, your outgoings, and the rent or mortgage you're still paying while you build, which lenders do count. And it has to sit inside a loan to value limit measured against the gross development value, the finished value of the house.
Specialist criteria usually come in two shapes. The higher-leverage product will fund up to around 80% of the land purchase, up to 80% of the build cost, and cap the whole thing at 80% of the finished value. The lower-leverage product will fund less of the land — around 65% — but up to 100% of the build cost, capped at 75% of the finished value. Which one wins depends entirely on whether your project is land-heavy or build-heavy, and it's the single most useful piece of arithmetic a broker does on a self build case.
On deposit: plan for roughly 20% to 25% of the total project cost, land plus build. And note that lenders normally expect your contribution to go in before theirs comes out, both on the plot and again on the build costs.
Most specialist lenders also allow interest only during the build, typically for up to 24 months, so you're not servicing a full repayment mortgage while also paying for somewhere to live. That clock usually starts at the first payment to you or your solicitor, not at the first brick, and at the end of it the mortgage converts to capital and interest unless you separately qualify for interest only.
The gross development value can move while you're building — the market shifts, or you change the plans or the materials. Lenders re-check the value at drawdown requests, and a fall can mean the next stage payment isn't what you expected. Tell your lender before you change the specification, not after.
If you already own the plot
This is the strongest position to apply from, and it changes the shape of the deal in your favour. The land counts towards your equity rather than being something you've to fund, you draw nothing until the build actually starts, and the funding tends to stretch further as a result. Some lenders will also lend against a plot you own outright to release cash towards the build itself.
If you've not bought the plot yet and it's going to auction, or planning hasn't been granted, that's a different job — see land bridging and pre-planning bridging finance. Take the plot with a bridge, get planning, then refinance onto a self build mortgage. Plenty of good projects run exactly that way.
What lenders will ask for
Self build applications are document-heavy. Getting the file straight before it goes anywhere near a lender is most of the work, and it's where a broker who knows the market saves you months. Expect to need:
- Full planning permission and the plans. Outline permission can get a decision in principle moving, but full permission is needed before a valuation
- Architectural drawings
- A full costed breakdown of the work and who is doing it — you, a contractor, or a mix
- A detailed cash flow budget, incomings and outgoings, with the contingency shown
- A structural warranty — NHBC or an equivalent recognised warranty — applied for before work starts, because the provider inspects at key stages. For conversions and renovations where a new build warranty is not available, a Professional Consultant's Certificate from a suitably qualified professional is usually accepted instead, but not for a ground-up build
- Building regulation approvals, which on some projects need to be granted before drawdown
- Contractors All Risk insurance with the lender's interest noted, typically with public and employer's liability cover of £5m each
- Your exit strategy, if any part of the loan runs interest only beyond the build
A JCT contract with your builder isn't always mandatory but lenders prefer it, mostly because it means you're invoiced in arrears and your cash flow gets some breathing room. Expect to give the lender a progress update at least every three months once you're building.
Self build mortgage or bridging: which fits?
The honest comparison. A self build mortgage is usually cheaper, priced like a mortgage rather than by the month, and needs no exit because it becomes your long-term loan. But it moves at mortgage speed, it's assessed on your income, and lenders want full planning, drawings and costings before funds flow. Bridging and development finance cost more but move in days, lend against the project rather than your payslip, and suit builds a mortgage lender won't touch.
- Time on your side, planning granted, income supports the loan: the self build mortgage usually wins
- Deadline, no planning yet, or income too lumpy to assess: land bridging or development finance, then refinance
- Building several units to sell rather than one home to live in: that is development finance, not self build
- Plenty of projects use both: a bridge to take the plot quickly, then a self build mortgage once planning lands
We're a mortgage broker as well as a bridging broker, which is the whole reason we can put the two quotes side by side instead of selling you the only one we can place.
Your questions
What is a self build mortgage?
A mortgage designed for building your own home. It's assessed on your income like any mortgage, but the funds release in stages as the build progresses rather than in one lump on completion day. When the house is finished it simply carries on as your long-term mortgage.
How much can I borrow on a self build mortgage?
Two limits apply at once. Affordability, exactly as on a normal residential mortgage, including any rent or mortgage you're paying while you build. And a loan to value cap measured against the finished value of the house — commonly up to 80% with specialist lenders, or up to 75% on products that fund a bigger share of the build cost.
How much deposit do I need for a self build mortgage?
Plan for around 20% to 25% of the total project cost, land plus build. If you already own the plot outright its value usually counts as your deposit, which can mean little or no new cash in. Lenders normally want your money in before theirs comes out.
Can I get a self build mortgage if I already own the land?
Yes, and it's the strongest position to apply from. The land counts as equity, you draw funds only as the build progresses, and some lenders will also lend against the plot to release money towards the build.
When do the funds actually arrive?
Normally at the end of each stage, after the work is done and checked. You fund each stage first, from savings or an overdraft facility, and the drawdown follows. Building that lag into your cash flow before you start is the difference between a smooth build and a stalled one.
Do you make full mortgage payments during the build?
Usually not. Most specialist lenders allow interest only during the build, typically for up to 24 months, then switch you to repayment once the home is finished. The 24 months normally runs from the first payment released, so it's a build deadline as well as a payment concession.
Can a first time buyer get a self build mortgage?
Yes, with specialist lenders. You don't need to have owned a home, and you don't need building experience either, provided the project has the right professionals around it: architect, contractor, warranty provider.
How do I get a self build mortgage?
Planning first — outline permission gets a decision in principle moving, full permission is needed before valuation. Then the file: architectural drawings, a full costed breakdown with contingency, the cash flow, and the warranty or professional cover for the build. A broker who knows which lenders actually like self build saves months here.
What are self build mortgage rates like?
Priced like specialist mortgages rather than by the month, so materially cheaper than bridging rates, but above a mainstream residential rate. The product fees, the valuation and the stage inspection fees matter as much as the headline rate on a build, so compare the total cost across the whole project, not the rate on its own.
What is the difference between self build and custom build?
On a custom build you buy a plot that already has outline or full planning and a developer provides the shell or the contracting, so much of the risk and the specification work is done for you. Lenders treat it as a self build variant, and because the costs are easier to pin down, budgeting is often more realistic.
Can I get one if I am self-employed?
Yes. Specialist self build lenders assess self-employed income as they would on any residential case — usually two to three years of accounts or tax calculations, sometimes fewer with a strong file. Lumpy or very recent self-employed income is the point at which bridging sometimes becomes the more realistic route.
Is a self build mortgage better than a bridging loan?
Cheaper and longer term, yes, but slower and income-assessed. Bridging wins on speed, on projects without planning, and on structures a mortgage lender won't touch. We place both, so you get the comparison rather than a sales pitch.
Building your own home?
Tell us the plot, the build cost and the finished value. We'll tell you honestly which product fits.
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