BUYING a house is stressful, not least the worries over how you’ll be able to afford your mortgage bill.
In an attempt to take some of the worry away, there has been a surge in the number of buyers rushing to take out ‘marathon mortgages’ – to make monthly repayments cheaper. But if you’re tempted, our expert Sarah Tucker, aka the Mortgage Mum, is here to talk you through the pros and cons – and her tips could save you tens of thousands in the long run.
Typically, borrowers usually take out a mortgage term of 25 years.
But a rising number of households are taking out ‘marathon mortgages’ – where the length of the term lasts 35 or even 40 years – as property prices rise.
The number of mortgages taken out with a term of 35 years or more have increased by 22.3 per cent over the past five years from 260,688 in 2021 to almost 320,000 in 2025, according to statistics from the Financial Conduct Authority (FCA).
The demographic driving the trend is those between 26 and 30.
The big draw of a marathon mortgage is that by stretching out the term of the loan, you make your repayments cheaper.
The average mortgage rate for a two-year fixed-rate deal is 5.61 per cent. If you took out a 25-year mortgage, borrowing £200,000 with this rate, your monthly repayments would be £1,242.
But stretching it to a 35-year term would shrink your monthly repayments to £1,089 – £153 less a month, or £1,836 over the year.
Sounds great, doesn’t it? But Sarah says taking one out without doing your research first could be an expensive mistake.
She says you could end up paying tens of thousands of pounds more in interest and may still be paying your loan off in retirement.
A worrying number of people could fall into this trap. Some 2,911 people age 41 or older took out a mortgage with a term of 35 years or more in 2025, up a huge 150 per cent from 1,160 on 2021.
Sarah’s a mortgage pro, having spent ten years working as a legal PA in London before qualifying as a mortgage broker in 2015 and launching The Mortgage Mum in 2019 – an award-winning, all-female mortgage and protection brokerage.
Sarah is now a regular mortgage expert on programmes including ITV’s This Morning, Sky News and BBC News.
She is passionate about making mortgage advice easy to understand and helping buyers make informed decisions about their homes and finances.
Follow her tips to understand whether a marathon mortgage could help you onto the property ladder – or cost you more in the long run.
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Cheaper repayments – but are YOU actually saving?
Having a longer mortgage term gives buyers the means to borrow more and buy a pricier home.
On the surface, this sounds like a win for first-time buyers struggling to afford property prices – with the potential to cut monthly repayments by hundreds of pounds.
For example, if you took out a £300,000 repayment mortgage at a 5 per cent interest rate over 40 years rather than 25, your monthly repayments would be £1,447 instead of £1,754 – £307 lower.
However, you need to weigh these up against the total cost – and there’s a big catch.
If the mortgage ran for the full term, you would pay £394,363 in interest compared to £226,131 over just 25 years – a difference of £168,232.
These figures are only an illustration, as your rate is likely to change when you remortgage too.
Moving home, switching lenders and making overpayments would also affect the final cost.
Sarah said: “With affordability under so much pressure, borrowers are looking for ways to make the monthly numbers work.
“Stretching your term allows you to do this, but it is always worth remembering that you will pay more interest over the long term.”
Apart from interest… What are the other drawbacks?
Another potential downfall of a marathon mortgage is that it will take you longer to build up equity in your property because more of your repayments will be swallowed by interest.
This means it will take you longer to reduce your loan-to-value (LTV) ratio, which could affect the mortgage rates available to you when it comes to remortgaging.
Lenders typically offer their best rates to borrowers with more equity in their home, so a slower build-up in equity could leave you paying higher rates for longer, making your mortgage even more expensive over time.
Sarah added: “If house prices fell significantly, having a larger outstanding balance could leave you more exposed to negative equity, so you shouldn’t rely on property prices going up to make the numbers work.”
Negative equity is when you owe more on your home than it’s actually worth.
It can happen if house prices take a tumble, or if you’ve barely made a dent in your loan – which is exactly the trap marathon mortgages can set.
This is because more of your early payments go towards interest rather than actually paying off what you borrowed.
Plus, lenders tend to run a mile from anyone whose home is worth less than they owe on it.
If you sell up, you might not even make enough to pay off your existing mortgage – leaving you with an awkward shortfall you’d need to cover from your savings, or worse, borrow even more to plug the gap.
Is a marathon mortgage right for me?
Taking out a longer term mortgage could be the difference between buying a home and not being able to.
Younger borrowers under 30 in particular could find the stretch is a useful way of getting on the ladder.
These buyers will in theory have plenty of time to reduce their mortgage term if their earnings increase or they build up more equity in their property.
Sarah said: “For a younger borrower or first-time buyer, a longer term can be a really useful stepping stone onto the property ladder, particularly if they expect their income to grow.”
Choosing a longer mortgage term could also improve your chances of passing a lender’s affordability assessment – but it doesn’t make it a certainty.
Sarah said: “Spreading the mortgage over a longer period reduces the monthly commitment used in the affordability assessment.
“But it isn’t a magic key to getting a bigger mortgage — lenders still look at your income, expenditure, commitments and overall ability to afford the borrowing.”
The mortgage expert said that having a longer mortgage term could also cause problems later on.
One of the big checks borrowers thinking about a marathon mortgage need to make is whether the term will continue into retirement and what age limits lenders impose.
Sarah said: “Some lenders are comfortable lending into retirement, but they’ll want to understand how the mortgage will be paid once you stop working — and age limits and criteria vary between lenders.
“Every lender has a different view on what income they accept beyond that retirement age.
“Some will accept pension income for example, others won’t.
“Some will take into account what type of job you do to make sure the retirement age seems sensible in line with.”
Can I shorten the term later?
You may be able to reduce the term when you remortgage if your pay rises or your other expenses fall.
Sarah said: “Whenever we advise a client on a longer-term mortgage, we would always encourage them to review the term at every remortgage opportunity, and we would also discuss overpayments.
“This is an excellent opportunity to review whether you are able to make higher monthly payments and shorten that term which is always the long-term goal.”
You could also make overpayments to clear the balance more quickly and reduce the interest you pay.
Many mortgage deals allow you to overpay by a certain amount – usually 10 per cent of your total balance – each year.
However, you should check the limit and whether early repayment charges apply, which typically range between 1 per cent and 5 per cent of your outstanding mortgage, before paying extra.
You may also need to pass a fresh affordability check if shortening the term would increase your required monthly repayments.
What are the alternatives?
A marathon mortgage is not the only way to reduce your monthly repayments.
Sarah said interest-only, or part interest-only mortgages are becoming more popular.
An interest-only deal can reduce the monthly bill because you are only paying the interest on the loan, not the original balance.
However, you will need a credible plan to repay the capital at the end of the term, and the eligibility rules can be stricter.
For example, if you have a £300,000 interest-only mortgage on a 25-year term at the average 5.61 per cent rate, you’ll only pay the interest you borrowed each month – nearly £1,403.
But, you’d still owe the lender the £300,000 cost of the original loan after the end of the 25-year term.
Consider speaking to an independent mortgage broker before choosing this option.
Three checks before committing to a marathon mortgage
Before signing up for a marathon mortgage, Sarah recommends asking yourself:
- Could I still afford the repayments if rates rose?
- Do I understand how much it could cost over the full term?
- What is my plan for shortening the mortgage later?
A marathon mortgage can be a useful way to make buying a home more affordable today.
But it should be part of a long-term plan – not simply a way to borrow more than you can comfortably afford.
