Stage 1: Finance & Feasibility

Why finance comes first

The most common self-build mistake is falling in love with a plot before knowing what you can afford to build on it. Land with planning permission is sold at a price that reflects what a developer would pay - and developers know their numbers precisely. Go in without a clear budget and you will either overpay for the land, underfund the build, or both.

Getting your finance in order first takes four to six weeks and costs nothing. It gives you a clear ceiling to work within, makes you a credible buyer when you make an offer, and means you can move quickly when the right plot comes up.

Step 1: Calculate your total budget

A self-build budget has six components. You need to fund all of them, not just the build cost.

• Land: Typically 20-42% of the completed property value depending on region. London and the South East are at the high end; the North East and Northern Ireland at the low end.
• Build cost: The cost of constructing the building. Typically £1,500-£3,500/m² depending on specification and build route.
• Professional fees: Architect, structural engineer, quantity surveyor, energy assessor, surveys. Allow 10-15% of build cost.
• Contingency: Unexpected costs. Allow a minimum of 15% of build cost - 20% if you are a first-time self-builder or managing trades directly.
• Insurance: Site all-risks, public liability, employers liability, structural warranty. Allow 1.5-2% of build cost.
• Planning and Building Regulations: Application fees, discharge of conditions, Building Control fees. Allow £3,000-8,000 depending on project complexity.

Use our Self-Build Cost Estimator to get a full breakdown based on your region and specification.

Step 2: Understand self-build mortgages

A self-build mortgage releases funds in stages as your build progresses, rather than as a single lump sum. This is fundamentally different from a standard residential mortgage and most high-street lenders do not offer them. You need a specialist lender.

There are two types of stage release:

• Arrears release: The lender releases funds after each stage is complete and inspected. You need enough cash or bridging finance to fund each stage before claiming it back. Lower interest costs overall.
• Advance release: Funds are released before each stage begins. Better for cash flow if you do not have large reserves. Interest accrues sooner.

Most self-build lenders will lend up to 85% of the total project cost (land plus build), subject to the completed property value supporting the borrowing. The maximum LTV varies by lender - some will go to 95% with Help to Build.

Use our Self-Build Mortgage Calculator to model your borrowing, LTV, and monthly payments across the full build.

Step 3: Get an Agreement in Principle

An Agreement in Principle (AIP) is a lender's conditional confirmation that they would consider lending you a stated amount, subject to full underwriting. It is not a formal offer but it tells you what you can borrow and demonstrates to land vendors that you are a serious buyer.

Get an AIP from at least two specialist lenders. The process typically involves a soft credit search (which does not affect your credit score), income verification, and an outline of your proposed project. Allow two to three weeks.

Specialist self-build lenders include Buildstore Mortgage Services, Ecology Building Society, Bath Building Society, Darlington Building Society, and Hinckley & Rugby Building Society.

Step 4: Check your credit file

Check your credit file with all three main agencies - Experian, Equifax, and TransUnion - before applying for any mortgage. Errors on credit files are more common than most people realise, and correcting them can take six to eight weeks. Do this early.

Lenders for self-build mortgages typically require a clean credit history. A small number of specialist lenders will consider adverse credit, but the rates are significantly higher.

Step 5: Register on your local authority's Self-Build Register

Under the Self-Build and Custom Housebuilding Act 2015, every local authority in England must maintain a register of people who want to self-build, and must grant sufficient development permissions to meet that demand within three years. Registration is free and gives you a legal right to be considered for self-build plots.

Most councils publish their registers online. Some also allocate serviced plots specifically for self-builders - these can be significantly cheaper than open-market plots with planning permission.

Help to Build

Help to Build is an equity loan scheme available in England for self-builds with an estimated completed value of up to £600,000. The government lends 5-20% of the total project cost (land plus build), which reduces the mortgage deposit you need. The equity loan is interest-free for the first five years.

You must have a self-build mortgage in place before applying, and the application must be made before you start building. The equity loan is repaid when you sell or remortgage, based on the property's value at that time.

VAT and the self-build advantage

Self-builders can reclaim VAT on eligible building materials under HMRC's DIY Housebuilders Scheme (VAT431NB). This is a one-time claim made after you receive your Completion Certificate, and must be submitted within three months of completion. The reclaim typically amounts to £15,000-40,000 on a standard self-build.

Crucially, keep every material receipt from day one. HMRC will not accept claims without original receipts, and there is no way to go back and obtain them later.

Read our full VAT Reclaim guide for the complete process, eligible items, and tips for maximising your claim.

Open a dedicated bank account

Open a separate bank account exclusively for your self-build project before you spend the first penny. This makes tracking costs accurate, makes the VAT reclaim straightforward, and makes it much easier to monitor your budget against actual spend throughout the build.