How a self-build mortgage is different
With a normal purchase, the lender releases the whole loan on completion because there is a finished house to secure it against. With a self-build, there is no finished house at the start, only a plot and a plan, so lenders release the money in stages tied to construction milestones.
This staged approach protects the lender, because the loan never gets too far ahead of the value being created on the ground. It also shapes how you manage cash flow, because you need funds available to keep the build moving between releases.
Self-build mortgages cover a range of projects, from building from scratch on a bare plot to major conversions and knock-down-and-rebuilds. The exact product and milestones depend on the lender and the project.
Arrears vs advance stage payments
The two ways self-build money is released, with different cash-flow effects.
| Feature | Arrears stage payments | Advance stage payments |
|---|---|---|
| When money is released | After each stage is finished and valued | At the start of each stage |
| Cash flow | You fund work first, then get reimbursed | Money is there before you spend it |
| Need for savings | Higher, to bridge each stage | Lower, easier on cash flow |
| Valuation | Each stage usually re-valued | Often pre-agreed amounts |
| Typical cost | Often slightly cheaper | Convenience can cost a little more |
Advance payments ease cash flow but may cost a little more; choose based on your reserves.
Typical self-build build stages
Money is commonly released around milestones like these.
| Stage | What it covers |
|---|---|
| Land purchase | Buying the plot (sometimes funded separately) |
| Foundations | Groundworks and foundations laid |
| Wall plate / superstructure | Walls up to roof level |
| Wind and watertight | Roof on, windows and doors in |
| First fix and plastering | Internal services and plastering |
| Completion | Final fit-out and certification |
Exact stages vary by lender and project; your lender confirms the milestones up front.
What lenders look for
Self-build lending is more involved than a standard mortgage:
- Detailed plans, costings and a realistic build timeline.
- Planning permission in place, or at least outline permission.
- A larger deposit, often 15% to 25% or more of total costs.
- Ownership of, or a firm purchase plan for, the plot.
- Evidence you can manage the project and any cost overruns.
- An appropriate warranty or architect's certificate for the finished home.
Budget for land and a contingency
You usually need to fund or secure the plot before building, and lenders rarely advance 100% of land plus build costs. Build in a contingency of at least 10% to 20% for overruns, delays and changes, because self-build budgets frequently stretch beyond the original estimate.
Mind the cash-flow gaps
With arrears payments you pay for each stage before the lender reimburses you, so you need accessible savings or short-term finance to keep contractors paid. Running out of cash mid-build is one of the most common reasons self-build projects stall.