The rise of marathon mortgages—home loans with terms extending beyond 35 years—is changing the way UK borrowers manage housing debt over the course of their working lives. More than 40% of new UK mortgage lending reportedly now has a term extending beyond state pension age, while mortgages longer than 35 years account for 11% of new lending.
The shift reflects pressure on household affordability. Extending a £300,000 mortgage from 25 years to 40 years can reduce monthly repayments by roughly 15% to 25%, but it also slows the pace at which borrowers repay principal. For some households, that means mortgage debt remains outstanding into their 60s or 70s.
The issue is becoming more significant as borrowers reach refinancing points. Lenders must consider whether income from pensions and other retirement sources can support repayments after employment income ends. The Financial Conduct Authority (FCA) has also identified later-life lending as an area requiring further market scrutiny, launching a 2026 study of lifetime and retirement interest-only mortgages. FCA
What Are Marathon Mortgages?
A marathon mortgage generally refers to a residential mortgage with an unusually long repayment term, commonly 35 years or more. Unlike a conventional 25-year mortgage, the longer structure spreads the same borrowing over a greater number of monthly payments.
The attraction is primarily affordability at origination. A longer term reduces the required monthly repayment because the principal is amortised over more years. However, the reduction in monthly payments does not mean the underlying borrowing becomes cheaper.
The outstanding balance can remain substantial for much longer, and the total interest paid over the life of the mortgage can increase depending on the interest rate and repayment pattern.
The trend is occurring within a wider UK mortgage market. Bank of England data showed that the outstanding value of residential mortgage loans reached £1,746.1 billion in the first quarter of 2026, while gross mortgage advances were £69.6 billion. Bank of England
How UK Marathon Mortgages Work
The mechanics are broadly the same as other repayment mortgages. Borrowers make regular payments covering both interest and principal, but the repayment schedule is stretched over a longer period.
For example, a £300,000 mortgage over 40 years requires the principal to be repaid over 480 monthly payments, compared with 300 payments on a 25-year term. Assuming the same interest rate, the longer term lowers the monthly payment but leaves the borrower paying interest for an additional 15 years.
This distinction matters when borrowers reach a fixed-rate renewal date.
A borrower who starts a long mortgage in their 30s may still have significant debt outstanding when approaching state pension age. At that stage, lenders can place greater emphasis on the sustainability and evidence of retirement income.
Employment income versus retirement income
During the working years, affordability assessments can rely heavily on salary, employment records or established business income.
Later in the mortgage term, the relevant income profile may include:
- State pension entitlement
- Occupational or private pension income
- Pension drawdown arrangements
- Annuity income
- Investment income
- Other verified retirement cashflows
The precise assessment depends on the lender and the borrower’s circumstances. A mortgage that was affordable when based on full-time employment income may require a different assessment once retirement becomes relevant.
Why Mortgage Terms Are Extending
Several factors are contributing to the growth of longer mortgage terms.
House prices and household affordability
Long mortgage terms can help borrowers qualify for a larger loan while keeping the initial monthly payment lower. This has particular relevance where house prices are high relative to household earnings.
Interest rates
The cost of borrowing also affects monthly affordability. Bank of England data showed that the effective interest rate on newly drawn mortgages reached 4.45% in July 2026, compared with 4.35% in June. Bank of England
When borrowing costs are materially higher than the ultra-low-rate environment of previous years, extending the repayment period can become one mechanism for reducing the monthly payment.
Loan-to-income constraints
Borrowers are also affected by income-based lending limits. In October 2026, the Prudential Regulation Authority introduced changes giving individual lenders greater flexibility over their high loan-to-income lending strategies, while retaining an aggregate 15% limit for high-LTI lending. Bank of England
Longer mortgage terms do not remove these constraints, but they can alter the monthly affordability calculation used alongside income and other financial commitments.
The Retirement and Remortgaging Problem
The most significant challenge for marathon mortgage borrowers may arise not when the original loan is approved, but when it reaches a refinancing point.
A borrower nearing retirement may have a shorter permissible mortgage term than they had when the original loan was taken out. Lenders can also apply maximum age limits or require evidence that the mortgage remains affordable from projected retirement income.
This can create a mismatch between the remaining mortgage balance and the borrower’s expected income.
For example, reducing the remaining term can increase monthly repayments because the outstanding capital must be repaid more quickly. At the same time, a borrower moving from employment to pension income may have less monthly cash flow available.
The outcome can therefore depend on several variables rather than age alone, including outstanding debt, property value, income, pension arrangements, interest rates and the lender’s criteria.
Costs and Financial Implications of Longer Mortgage Terms
The central trade-off is between monthly affordability and the speed of debt repayment.
A 40-year mortgage can produce substantially lower monthly payments than a 25-year mortgage for the same principal and interest rate. But the borrower makes payments for longer and generally pays more interest over the full term.
The effect can be particularly important when interest rates change.
A fixed-rate mortgage provides payment certainty during the fixed period, but the borrower normally needs to refinance or move to another rate when that period ends. If the remaining term is long and the outstanding principal is still significant, the cost of refinancing can materially affect household finances.
The Bank of England reported £34,500 in remortgage approvals in July 2026, up from £34,100 in June. Bank of England
That refinancing market is therefore an important part of understanding the longer-term implications of extended mortgage terms.
Retirement Interest-Only Mortgages and Later-Life Lending
Retirement Interest-Only (RIO) mortgages are one mechanism within the UK’s later-life lending market, although they operate differently from conventional repayment mortgages.
Under an RIO mortgage, the borrower generally makes monthly interest payments while the capital is repaid following a specified life event, commonly the sale of the property. The FCA introduced the regulatory framework for RIO mortgages in 2018. FCA
The FCA’s rules require firms considering certain RIO arrangements to assess whether the product is appropriate for the customer’s circumstances. The regulator also requires relevant information about potential alternatives and the implications of the product to be communicated to customers. FCA Handbook
RIO mortgages are therefore not simply longer versions of standard repayment mortgages. They represent a distinct form of later-life lending with different repayment mechanics and affordability considerations.
The FCA’s 2026 Later Life Mortgages Market Study is examining the lifetime and RIO mortgage sectors, including whether changes are needed to allow the market to respond to changing consumer needs while maintaining competition and consumer protection. FCA
Risks and Limitations of Marathon Mortgages
Long mortgage terms can address an immediate affordability constraint, but they introduce several longer-term considerations.
Higher lifetime interest costs: Keeping the balance outstanding for additional years can increase total interest paid.
Retirement exposure: A mortgage extending into retirement creates greater dependence on pension and other post-employment income.
Refinancing risk: The affordability assessment at a future remortgage may differ from the assessment made when the mortgage was originally approved.
Age-related lending criteria: Lenders can apply different criteria to older borrowers, potentially limiting the available term or product range.
Interest-rate risk: A borrower coming off a fixed rate may face different payments when refinancing, depending on prevailing rates and the new product.
Property-sale dependency: Some later-life mortgage structures rely on the eventual sale of the property to repay capital. Property values and selling conditions can therefore become relevant to the repayment outcome.
These risks do not mean that a longer mortgage is inherently unsuitable. They demonstrate why the structure needs to be considered across the entire expected life of the borrowing rather than solely on its initial monthly payment.
UK Mortgage Market Outlook
The regulatory environment is evolving alongside the later-life mortgage market.
In June 2026, the FCA proposed changes intended to reduce some barriers affecting older borrowers, including reforms concerning retirement interest-only mortgages. The regulator said the proposals would maintain responsible lending requirements and the obligation for firms to assess affordability. FCA
The FCA’s separate Later Life Mortgages Market Study indicates that retirement lending is becoming a distinct regulatory and market-policy issue rather than a niche segment. FCA
At the same time, broader mortgage conditions remain influenced by interest rates, household income, property prices and lending standards. The increasing prevalence of longer terms means these factors will increasingly intersect with retirement planning and refinancing.
The key question for lenders and regulators is therefore not simply how many mortgages extend beyond traditional retirement ages, but whether the market has adequate mechanisms to assess and manage those loans as borrowers move from employment income to retirement income.
Conclusion
The expansion of marathon mortgages reflects the UK’s changing affordability landscape. Terms of 35 years or more can reduce monthly repayments and make borrowing more manageable at origination, but they also extend the period over which households carry mortgage debt.
For borrowers whose terms reach retirement age, the critical point may come years after the original mortgage is approved. Refinancing can involve a different income profile, a shorter permitted term and greater reliance on pension or investment income.
Regulatory developments in 2026, including the FCA’s work on later-life mortgages and retirement interest-only lending, suggest that the treatment of older borrowers is becoming a more prominent part of UK mortgage-market policy. The longer these mortgages remain a feature of new lending, the more important the transition from employment-based affordability to retirement-based affordability becomes.
