Falling house prices would make the cost of the majority of improvements greater than the increase in the value of a property.
The research shows that extensions or new kitchens would leave home owners with five-figure losses if they put up their property for sale immediately after carrying them out.
Phil Cliff, director of Abbey Mortgages, said: "Our research shows that very few home improvements will actually add more value than they cost, so it's important that people make these improvements because they want to live in the end result and not to add value alone."
Sellers who added an extension would boost the house price by £13,500, but it would cost nearly £34,000. They could be £9,600 out of pocket if they carried out a basement or loft conversion.
Sellers would only recoup their investment on cosmetic changes, such as painting. The research estimated that people who spent £1,330 sprucing up their properties could increase its sale price by more than £3,500.
