Architects and planners need to radically rethink housing policy for older people as the number of Britons over the age of 85 is set to nearly double in the next 25 years, a prominent social historian has said.

“The great issue for public policy now is to choose whether to regard the growing population of older people in the UK as a medical/custodial ‘problem’ or as a civic issue – how we keep older people integrated into the life of the community,” Ken Worpole, an academic and writer on architecture, planning and social policy, told the Observer.

His comments followed the release of data by the Office for National Statistics last week showing that the number of over-85s in the UK is set to increase from 1.6 million in 2018 to 3 million by 2043.

According to Worpole: “If the 20th century was the century of the child, then the 21st century is the century of the elderly.” But politicians prefer to treat older people as a medical issue, he said. “Spending money on medicalisation is simpler – politicians find it easier to spend money than think creatively – than building resilient communities that regard older people as important citizens.”

Institutionalised care homes are increasingly rejected by many people in favour of “ageing in place”, which allows continued engagement in local communities.

A new almshouse movement, advocated by some experts, builds on a way of living dating back to the 10th century. Almshouses provide sheltered but independent housing, often around a central courtyard, at affordable rents. Many offer social activities, on-site maintenance and – crucially – links with external groups.

Worpole has been involved with the development of a new almshouse in Bermondsey, south London, for United St Saviour’s, a 500-year-old charity. Construction is due to begin next spring and completed by the autumn of 2021.

The project, says Worpole, “seeks to actively retain longstanding entanglement of residents with the life of the neighbourhood, old friendships, local parks, libraries, shops and social activities. It is open to the world and still part of everyday life.”

The site of the new homes is on a busy high street, and designed to be accessible to the general public. A glass-fronted “community lounge” will be available to local groups.

Stephen Witherford, of the project’s architects Witherford Watson Mann, said: “At the moment, older people tend to be moved to the margins of towns and cities, dislocating them from communities. Many die a social death before physical ailments kick in.”

Older Women’s Co-Housing (OWCH) in Barnet, north London. Photograph: OWCH

Another radical approach is the Older Women’s Co-Housing (OWCH) project in Barnet, north London, which provides 25 flats to women aged between 53 and 90. It was completed three years ago and is run as a collective, with all residents involved in decision-making.

“Older people need to be encouraged to think about how they want to live their lives, and then take charge of that,” said Angela Ratcliffe, a resident. “The longer you’re in charge of your life, the mentally fitter you are. If you’re passive, there’s a danger of giving up.”

According to Silver Cities: Planning for an Ageing Population, a report by the Grosvenor property group, the proportion of over-65s in the global population will reach 25% by 2045.

“Many older Londoners are living alone in the family four-bedroomed home that they raised their children in, but which may not be suitable for an older person,” says the report.

The housing industry should “focus on building communities made up of homes for rent that will meet the needs of all demographics and not just the 25- to 35-year-olds whose faces often adorn modern development hoardings.”