How Self Build Mortgages Differ
Instead of one lump sum on completion day, a self build mortgage releases funds in stages as the build progresses. Typical stages run: land purchase, foundations, wall plate, wind and watertight, first fix and plastering, and completion. At each stage the lender, usually via a valuer, confirms progress before releasing the next tranche.
The critical distinction is between the two payment types. Arrears stage payments release money after each stage is built: simpler and more common, but you fund each stage up front and are reimbursed, which demands working capital. Advance stage payments arrive before each stage, protecting your cash flow. Fewer lenders offer this and it usually costs a little more, but for families without large reserves it is often what makes the project viable.
What Lenders Will Offer
Expect to borrow up to around 75 to 85 percent of land and build costs with mainstream self build lenders, with some specialist and broker-arranged products stretching further on the build element. Rates during the build phase are higher than standard mortgages, and most people remortgage onto a conventional product once the home is complete and valued.
The lending market here is specialist territory: smaller building societies, dedicated self build products, and brokers who work this niche daily. Two documents move every lender conversation forward: credible costings and a clear programme. This is exactly what our Opinion of Probable Cost provides at the very start of the Mosaic Bespoke process, an experience-based cost assessment a lender can take seriously, before you have spent significant money on design.
What Lenders Will Insist On
Planning permission, in place or clearly achievable, before full approval. A structural warranty or professional consultant’s certificate on completion, without which the exit remortgage and any future sale become difficult; our guide to new build warranties covers the options.
And a credible builder and contract. A single accountable design and build team with a fixed process is easier to lend against than a self-managed project with separate trades, and it shows in the questions lenders ask.
Start with the number every lender wants to see: a free appraisal including an Opinion of Probable Cost for your site and brief.
The Financial Advantages Self Builders Forget
VAT. New self build homes are effectively zero-rated: you reclaim the VAT on eligible materials and most labour is zero-rated to you, through the DIY Housebuilders Scheme. On a substantial build this is tens of thousands of pounds, and the paperwork discipline starts on day one, not at the end.
CIL exemption. Self builders can claim exemption from the Community Infrastructure Levy, a significant charge in many Hertfordshire districts, provided the exemption is secured before commencement and the rules are followed exactly. Get the timing wrong and the exemption is lost, so it sits on our pre-construction checklist, not as an afterthought.
Stamp duty. You pay duty on the land you buy, not on the finished value of the home you create. On a bespoke home in this part of the world, the difference is rarely small.
Sequencing the Money and the Project
The builds that run smoothly are the ones where finance, planning and construction were planned as one sequence. Costings first, so borrowing is sized correctly. Planning strategy second, because approval unlocks lending. Then a coordinated technical package, so stage valuations pass without drama and funds release on time.
That is the shape of our four-stage process, and it is as much a financial de-risking tool as a construction one. For the underlying numbers, our guides to the cost of building a house in our four counties and what cost per square metre really means are the natural next reads.
*This article is general information, not financial advice. Speak to a regulated mortgage adviser about your circumstances.*
Lenders back certainty. A credible cost plan and one accountable team change every conversation.
Key takeaways
- Self build mortgages release funds in stages, in arrears or in advance, and the choice shapes your cash flow.
- Expect up to 75 to 85 percent of costs, higher build-phase rates, and a remortgage at completion.
- Lenders insist on planning, a warranty route and a credible builder before they commit.
- VAT reclaims, CIL exemption and land-only stamp duty are worth tens of thousands on a bespoke home.
- Sequence costings, planning and technical work in that order and the funding follows cleanly.
About the author
Kevin Edge founded Mosaic Bespoke and has spent more than two decades in planning, design and construction, working with private clients and landowners across Hertfordshire, Buckinghamshire, Bedfordshire and North London.