An estimated 10,000 applications to create garden annexes are being made to councils per year, according to calculations from a home insurer.
As well as adding some much-needed space, some home owners may be making such applications with a view to adding value to their property.
Churchill Home Insurance, which calculated the figures, said research among estate agents suggests that three and four-bedroom homes with a garden annexe can potentially command asking prices as much as 27% higher than similar nearby properties.
The extent to which garden annexes could add any value would depend on local housing market conditions, so home owners considering this may want to research the cost of moving versus improving – and the value any improvements could add – in their own area.
Churchill’s research also suggests that around eight in 10 (82%) applications for garden annexes are successful.
Around seven in 10 applications are for new garden annexes, built from scratch, with the remainder being for ones to be converted from an existing outbuilding or shed.
Churchill made the calculations after making freedom of information requests to 392 local councils across the UK, of which around a quarter provided usable data.
It also analysed research among 100 estate agents from across the UK to calculate how much a garden annexe might add to the value of a property.
Craig Rixon, head of Churchill Home Insurance, said: “Developing your own, new or converted garden annexe can be a very exciting process and is becoming ever more popular as people get increasingly savvy about home renovations.
“Whether you’re building an annexe for an older relative or just for the additional space, it is often a cheaper and easier alternative than moving to a larger property.”
He continued: “It is important that you inform your insurer of any home renovations you plan to make so that your home and its contents are adequately insured during the course of the renovation and upon completion.”