On average, 23 per cent of homeowners have converted living space into an additional bedroom, with a quarter of respondents making these adaptations within the last two years, the lender found.
Alongside bedrooms, building outhouses in the garden, ground floor bathrooms and step-free access to the home were all noted as necessary improvements when living in an inter-generational household, with one in ten homeowners expecting that they will one day be taking care of their elderly parents in their home.
The report revealed that across the country the distribution of inter-generational families differs, with more people living with adult relatives in cities such as London or Birmingham, with increasing housing costs likely to be a contributing factor.
Londoners are most likely to live in a multi-generational home, with 35 per cent currently in this situation, while East Anglian residents are the least likely to live with adult family members.
Property prices holding firm in city centres and dropping elsewhere is thought to be a key factor in this national split.
Hannah Bernard, head of Barclays Mortgages, said: “As more of us are living with several generations under one roof, it’s interesting to see how, as a nation, we are adapting our properties to the changing needs of our homes.
“If you live in a multi-generational home or expect to in the future, it’s important to think about whether you need more space in a new property or if you can simply adapt your home to suit your needs.
“We understand the factors that need to be considered in these circumstances and want to help families stay in control of their finances as they plan for a change in their home – whether it’s a big move, a re-mortgage or home improvements.”