Last reviewed: June 2026
TL;DR- Self build mortgages release funds in stages as construction reaches defined milestones rather than as a single completion payment.
- Two main structures exist: arrears-based (funds released after each stage is certified) and advance-based (funds released before each stage begins).
- Borrowers need to fund the land purchase separately or include it in the mortgage - not all lenders include land in the self build finance.
- The Help to Build equity loan scheme (check current availability on GOV.UK) supports self builders with access to smaller deposits.
How Self Build Mortgages Work
A self build mortgage is a specialist loan designed for borrowers who are building their own home rather than purchasing an existing property. Instead of releasing the full loan at completion (as a standard residential mortgage does), a self build mortgage releases funds in stages as construction progresses through defined milestones.
The lender appoints a valuer who inspects the property at each stage and certifies that the work has been completed to the required standard before the next tranche of funds is released. The borrower typically pays interest only on the funds drawn down to date during the construction period, switching to a repayment mortgage once the build is complete and the property is habitable.
Arrears vs Advance Stage Release
Self build mortgages operate on one of two stage release structures:
- Arrears release: funds are released after each build stage is completed and inspected. The borrower funds each stage from their own resources first, then receives the mortgage tranche to replenish their funds. This requires sufficient capital reserves to fund each stage upfront before reimbursement.
- Advance release: funds are released before each stage begins, allowing the borrower to use the mortgage funds to pay contractors and materials costs. This requires less upfront capital but is offered by fewer lenders and typically at higher rates.
The choice between arrears and advance release depends on the borrower's capital reserves and cash flow capacity. Borrowers without significant savings may need an advance release mortgage to fund the build without running out of capital mid-construction.
Typical Build Stages
Stage release schedules vary by lender but commonly include: land/site purchase; foundations complete; wall plate level (superstructure complete to eaves); wind and watertight (roof on, windows and doors fitted); first fix (electrical, plumbing, internal frame); second fix and plastering; and practical completion. Each stage triggers a valuer inspection and fund release.
Budgeting for Self Build
Self build projects frequently encounter cost overruns due to unforeseen ground conditions, material price changes, contractor delays or specification changes. Most lenders require the borrower to demonstrate a contingency budget of at least 10-15% of the build cost to protect against overruns. Running out of funds mid-build is a serious risk - a partially constructed property is difficult to sell or remortgage and the lender may take enforcement action.
Stamp Duty on Self Build
Stamp duty land tax on a self build applies to the land purchase price at the land acquisition stage. No SDLT is payable on the construction costs themselves. First time buyers may qualify for SDLT relief on the land purchase, subject to the purchase price cap and standard eligibility criteria.
Frequently Asked Questions
Can I include land purchase in a self build mortgage?
Some self build lenders include the land purchase as part of the overall self build facility; others require the land to be purchased separately, potentially with a bridging loan, before the self build mortgage is taken. The approach depends on the lender. Including land in the self build mortgage simplifies the process but requires the lender to be comfortable with the overall project from inception.
What insurance do I need during a self build?
Self build projects typically require: site insurance (public liability and employer's liability if contractors are on site); structural warranty insurance (most lenders require this - common providers include NHBC, Premier Guarantee and Architects Certificate schemes); and contract works insurance covering the build in progress against damage, fire and theft. Standard home insurance does not cover a property under construction.
Is planning permission required before applying for a self build mortgage?
Yes. Most self build lenders require planning permission (full planning permission, not outline permission) to be in place before the mortgage is approved. Some lenders consider applications with outline planning permission, but full planning is generally required to proceed. Planning permission confirms that the proposed development is acceptable to the local planning authority and reduces the lender's risk.
Can I live on site during the build in a caravan?
Living on site in a caravan or temporary accommodation during the build may require planning permission from the local authority - this is a separate consideration from the planning permission for the build itself. Self build lenders are not directly affected by the borrower's living arrangements during construction, but the borrower should ensure they have adequate accommodation and that any temporary site living is legally permitted.
