Britain has produced a ‘boomerang’ generation twice as likely as their counterparts in the rest of Europe to come back to live in the family home. Research shows that, every year, 4% of 16–29 year olds who have moved away return to live with their parents, double the number in France, Ireland and Greece.

The boomerang phenomenon, precipitated by 20- and 30-somethings frustrated by a lack of mortgages, precarious careers and rising living costs, could remain with us for several years. ‘Although prices have fallen substantially from their peak in 2007 and continue to decrease, redundancies and the difficulty securing mortgages is strengthening the family’s instinct to pull together,’ believes house-finder Jonathan Haward from County Homesearch.

One way that parents can cope with loud music and late nights from their thwarted independent young is to extend the family home to accommodate boomerang returnees. Michael Wilson from Michael Wilson Restorations, a Surrey-based company specialising in projects like these, thinks the first and cheapest option is to convert the attic at about £200 a square foot. Even if you’re on a tight budget, ‘it’s better to run stairs up, rather than installing a flimsy retractable loft ladder,’ he advises.

Mr Wilson, who has a boomerang son who flew back after university, says the problem isn’t finding somewhere for your offspring to sleep, but space for your child’s friends when they turn up for holidays. He’s chosen the more costly option, at about £100,000, of converting an 800sq ft basement, providing an extra reception/media room and guest suite with shower and kitchenette. ‘Subterranean rooms are in vogue,’ Mr Wilson says. ‘At about £300 a square foot, where property is worth £500–£700 a square foot, it only costs half the amount to create them compared with moving house.’

A question of rent

Tim Harriss from Knight Frank, Guildford (01483 565171) is selling the principal part of Busbridge Hall near Godalming, also restored by Michael Wilson. By digging down, a lower-ground floor with three extra bedrooms and two bathrooms has been created for boomerang progeny.

Keeping the master suite away from other bedrooms, as at Busbridge Hall, is one way to survive chicks returning to their nesting ground. If you can have separate entrances, so much the better. Mr Harriss also notes a trend in building self-contained flats above garages. ‘Although it can cost about £50,000, it’s cheaper than selling and moving somewhere larger.’

The thorny question of rent is best avoided by parents, who prefer their children living rent-free and accumulating money for a deposit quickly, thus exiting the family home as soon as possible. If you insist on charging rent, expect anything from £75 to £100 a week. You can rent out a room for £350 a month (£4,250 a year) tax free under Government guidelines a strong selling point when marketing your converted home with added accommodation.

But letting your children reside in a wing of your home might not be the wisest policy, argues James Greenwood from Stacks Property Search and Acquisition. ‘Before you spend £30,000 to £40,000 on a loft or garage conversion, consider the long-term benefits of using that capital to help your children acquire their first home. ‘The difference between this recession and previous recessions is that money is cheap, especially if you can help out with a sizeable deposit.’

Beating the boomerang blues

* Good sound insulation prevents many a row

* An external entrance to a basement allows offspring independence

* Renovations needn’t be luxurious you don’t want yourissue to stay forever

* Adding extra space can increase the value of your home when you sell