A beautiful design is only buildable if it is funded properly, all the way to the end. Here are the realistic ways people pay for a build, extension or renovation, and how to avoid running out of money halfway.
Before you look at how to fund it, work out what the whole thing really costs. Most budget failures start here.
The build cost is only part of the picture. Your true number is the build cost plus professional fees, plus VAT where it applies, plus a proper contingency of around 10 to 15 percent. Fund the whole of that, not just the headline build price. A project that is funded to 90 percent of its real cost is a project in trouble.
The simplest route, and the cheapest, is to pay for the work as it happens.
If you have the funds, paying against stage payments as the build progresses avoids all borrowing cost. A good contractor works to a clear, costed programme with payments tied to progress, so you always know what is due and when. Even if you are borrowing, keeping a cash buffer for the contingency is wise.
For most extensions and renovations, borrowing more against your home is the usual route.
A further advance from your existing lender, or a remortgage to a new one, releases equity from the home to fund the work. For a typical extension, many people only need a modest top-up, and a further advance keeps their existing rate in place. A mortgage adviser will compare the options and the total cost.
For a new build or a major project, a specialist self-build mortgage releases money in stages as the work is done.
Self-build lending is released in tranches at set stages, typically land purchase, foundations, wind and watertight, first and second fix, and completion. Two structures exist:
Expect to need a deposit of around 25 percent of total land and build costs, with interest charged only on what you have drawn while the build is live. A specialist self-build broker is worth their fee here.
Short-term, property-secured borrowing that bridges a timing gap. Powerful, but to be used with care.
A bridging loan is secured against property, charges interest monthly (roughly 0.55 to 1.5 percent a month in 2026 depending on the deal), and is repaid in full at the end of the term. It suits a genuine timing gap, for example funding work before a sale completes. It is expensive relative to a mortgage and needs a clear exit plan, a sale or a remortgage, before you take it on.
The difference between a calm project and a stressful one is usually the buffer you kept back.
Never start a build you cannot finish. Secure the full funding, including fees, VAT and contingency, before you break ground. A half-funded project stalls, and a stalled project costs far more than it saves.
We give you a fully costed programme with staged payments tied to real progress, so your funding can be arranged with confidence and drawn down in step with the build. Clear costing up front is what lets you borrow or budget the right amount, and keep the project moving to completion.
This is general guidance, not financial advice. Speak to a qualified mortgage or financial adviser about the right funding for your circumstances.
General guidance for 2026, written for homeowners in Surrey and Hampshire. It is a summary, not professional advice; confirm the details for your specific project.
We will give you a clear, itemised programme so you know exactly what to fund, and when, before you commit.