A self-build mortgage is a specialist mortgage that helps you buy a plot of land and pay for the construction of your own home. Unlike a standard residential mortgage, the lender usually releases the money in stages as the work progresses instead of paying the full amount at once.

Reviewed on. As an example, one lender may require a 20% deposit for the land and a further 15% to 20% of the build costs to be available before construction starts. These figures are not universal.

Self-Build Mortgages at a Glance

Feature How a self-build mortgage works
Purpose Buying land and funding the construction of a new home
Payment method Funds are released in stages
Mortgage type Usually a specialist residential mortgage
Lender assessment Your income, outgoings, plans, planning permission, build costs and expected property value
Deposit Varies by lender and project. You may also need cash for early construction costs
Main risk Running out of money between construction stages

How Does a Self-Build Mortgage Work?

A self-build mortgage usually works through the following stages:

  1. You identify a suitable plot and prepare your plans.
  2. You obtain planning permission and calculate the expected construction cost.
  3. The lender checks your affordability and the project's financial viability.
  4. The lender releases the mortgage in stages, which may follow milestones such as buying the land, completing the foundations, reaching the watertight stage and finishing the property.
  5. The lender or its valuer inspects the work before releasing further funds.

The payment schedule varies between lenders. Some base payments on construction milestones, while others link them to the property's increasing value.

What Are Advance and Arrears Self-Build Mortgages?

The two main types are advance stage payment mortgages and arrears stage payment mortgages.

Advance Stage Payments

An advance mortgage releases money before a stage of work begins. This can help when builders or suppliers require payment upfront.

Advance payments may make the project easier to manage, but not every lender offers them. The mortgage may also have different fees, rates or lending limits.

Arrears Stage Payments

An arrears mortgage releases money after a stage of construction has been completed and inspected.

For example, you may need to pay for some early groundwork yourself before the lender releases the next part of the mortgage. You therefore need enough savings or other funding to cover the deposit and initial construction costs.

For most self-build projects, cash flow matters as much as the interest rate. A mortgage can look affordable overall but still cause problems if the lender does not release money when your contractor needs to be paid.

What Can a Self-Build Mortgage Pay For?

A self-build mortgage may help pay for:

  • The purchase of a building plot
  • Groundworks and foundations
  • Materials and labour
  • Professional fees
  • Construction at different stages
  • Some other project costs

Lenders do not all cover the same expenses. You may need separate savings for planning fees, architectural work, surveys, legal costs, building regulation fees, inspections and other charges.

How Much Deposit Do You Need?

There is no standard deposit for every self-build mortgage. The amount depends on the lender, the plot, your income, the projected value of the finished property and whether you already own the land.

For example, Ecology Building Society says applicants may need a minimum 20% deposit for the land, along with a further 15% to 20% of the build costs available to start construction. Other specialist products use different maximum loan-to-value limits, so these figures should not be treated as general rules.

If you already own the land outright, you may need less cash for the plot. The lender will still assess the land's value and your ability to pay for the early construction work.

What Does a Lender Look At?

A self-build mortgage application usually requires more information than an application to buy an existing home. The lender may ask for:

  • Proof of income and regular outgoings
  • Bank statements and identification
  • Planning permission
  • Detailed architectural plans
  • A breakdown of labour and material costs
  • Details of your builder, architect or project manager
  • The expected value of the completed home
  • Information about the construction method
  • Evidence of contingency funds

Some lenders restrict the materials or construction systems they accept. The completed property must provide suitable security for the mortgage and be capable of being sold in the future.

What Extra Costs Should You Budget For?

The mortgage covers only part of the project. Other costs may include:

  • Land transaction costs
  • Solicitor's fees
  • Planning application fees
  • Architect's fees
  • Structural engineer fees
  • Surveys and valuations
  • Building regulation charges
  • Interim inspection fees
  • Insurance
  • Temporary accommodation or rent
  • Utility connections
  • A contingency fund for unexpected work

BuildStore gives typical professional and project fees of about £10,000 to £20,000 in some cases. It also recommends allowing a contingency of around 10% to 20% of the build budget. These are indicative figures, not fixed costs for every project.

What Are the Advantages and Disadvantages?

Advantages

  • You can design a home around your needs.
  • You may be able to finance both the plot and the construction.
  • Staged payments mean you do not need to borrow the full amount immediately.
  • Some products allow interest-only payments during the build, subject to eligibility.
  • A specialist lender may accept modern or non-standard construction methods.

Disadvantages

  • The application is more involved than a standard mortgage application.
  • You may need substantial savings before construction begins.
  • Delays and rising material or labour costs can create funding problems.
  • The lender may delay or reduce a payment if the project does not meet its conditions.
  • Specialist mortgages may have different fees, rates and valuation requirements.
  • With an interest-only arrangement, you need a clear plan to repay the capital. MoneyHelper warns that interest-only borrowers remain responsible for repaying the full amount borrowed at the end of the mortgage term.

Is a Self-Build Mortgage Right for You?

A self-build mortgage may be suitable if you have:

  • A specific plot or land purchase in mind
  • Planning permission or a realistic route to obtaining it
  • Detailed plans and professional costings
  • An income that meets the lender's affordability assessment
  • Savings for the deposit, fees and early-stage work
  • A contingency fund for unexpected expenses

It may be unsuitable if your budget is already fully committed, your build costs are unclear or you cannot pay for work before an arrears-based lender releases funds.

Self-Build Mortgage vs a Standard Mortgage

A standard mortgage usually finances an existing, habitable property. The lender releases the money when the purchase completes.

A self-build mortgage finances a construction project. The lender assesses both the borrower and the proposed home, then releases the funds as the project progresses. This staged payment structure is the main difference between the two mortgage types.

Bottom Line

Before buying a plot, check more than the interest rate and maximum loan amount. You also need to understand:

  • When the lender releases each payment
  • How much money you need upfront
  • Which construction methods the lender accepts
  • What happens if the build costs increase
  • Whether you can repay the mortgage if the project is delayed

Have your plans, planning position, costings and funding structure reviewed by a specialist self-build mortgage adviser before you commit to the plot.