This guide provides general information and is not a substitute for personalised mortgage, tax or legal advice.
Written and reviewed by the Highhouse Money mortgage team · Last reviewed: 25 August 2026
When you buy a finished house, the deposit is paid once, at completion. A self-build works differently. Money is lent in stages as the project progresses, so your own contribution is needed at several points: when buying the land, and throughout construction until the lender's next release.
This guide concentrates on that cash side of self-building. It is general information, not financial advice, and does not quote lending percentages because they vary by lender and project.
To plan your contribution, gather
- The plot price, or its value if owned
- A detailed build cost estimate
- The planned build stages and timings
- Warranty, design and professional fees
- Current savings and releasable equity
- Living costs during the build
Why deposits look different on a self-build
Lenders limit how much they will advance against the land and against the value of the work completed at each stage. The gap between what they release and what each stage actually costs is what you fund yourself. Over the whole project those gaps add up to your total contribution.
That means two households with the same total deposit can have very different experiences, depending on when the cash is required and whether it is available at that moment.
Arrears and advance releases
| Arrears release | Advance release | |
|---|---|---|
| When funds arrive | After a stage is completed and valued | At the start of a stage |
| Cash you need to hold | Higher — you pay first | Lower — funds come first |
| Risk of stalling | Greater if cash is tight | Reduced, subject to conditions |
| Typical checks | Valuation after each stage | Valuation and cost evidence |
General features only; product terms and availability vary.
Where your contribution can come from
- Cash savings built up before the project
- The value of land you already own
- Equity released from your existing home
- Proceeds from selling your current property
- Gifts from family, subject to lender rules
Each source has knock-on effects. Selling first can mean renting or temporary accommodation, while keeping your current home means carrying its costs alongside the build.
Building a realistic cash-flow plan
Map the project stage by stage: groundworks, wind and watertight, first fix, second fix and completion are common milestones. For each, set out the expected cost, the likely lender release and the date you need the money. The shortfalls show where your own funds are needed and how much must be accessible at once.
Add a contingency for overruns and price changes, and remember professional fees and the warranty often fall due early, before significant lending has been released.
This is general information, not financial advice. Your home may be repossessed if you do not keep up repayments on your mortgage.
How advice helps
Self-build lending is a niche, and products differ in how they release funds, what they accept as your contribution and which warranties they require. Comparing those details against your cash-flow plan early — ideally before buying the plot — can avoid the most common problem: running out of money between stages.
Frequently asked questions
What counts as my deposit on a self-build?
Your contribution usually covers part of the plot purchase and part of each build stage. If you already own the land outright, its value can often count towards your contribution, reducing the cash needed. Exactly how much you must put in depends on the lender and product.
What is the difference between arrears and advance stage payments?
With arrears stage payments, the lender releases money after each stage is completed and valued, so you fund the work first and are reimbursed. With advance stage payments, money is released at the start of a stage, which reduces the cash you need to hold but may come with different conditions.
Can I use equity in my current home as a deposit?
Some self-builders remortgage their existing home or sell it and rent during the build. Either can release funds, but each has costs and risks, including carrying two sets of borrowing or rental costs while you build.
Do I need a contingency fund on top of the deposit?
Build costs frequently run over, and lenders only release funds against valuations. Holding a contingency, separate from your planned contribution, reduces the risk of a project stalling between stages.
Does a self-build need a warranty to release funds?
Most lenders require a structural warranty or an architect's certificate so that the finished home is mortgageable. It usually needs arranging before work starts, and its cost should be included in your budget.
Sources and further reading
Where figures or rules can change, the position described is correct at the time of writing (25 August 2026) — always check the linked authoritative source for the latest position.
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