Brits are wasting billions of pounds on tasteless home improvements that actually reduce the value of their home.

Laying cheap wooden flooring and installing PVC windows are among the design crimes that are knocking thousands of pounds off the value of their homes.

Removing period features and installing budget kitchens and bathrooms can knock as much as £9,637 off the price of an average house, research by Direct Line Home Insurance shows.

In co-operation with property experts, the insurer identified the ‘home improvements’ most likely to reduce the value of a property, and found that more than 20 million Brits had carried them out.

But nearly half of those making changes mistakenly believe they will add value to their property, with one in ten believing they will add more than £10,000.

Changes to gardens can also prove costly. According to Habitus, the 1.8 million homeowners digging fishponds in their gardens could lose £3,854 on average, as will those concreting over their front gardens.

“Taste is a subjective thing, but our research does who that certain home improvements have detrimental effect property values,” said Direct Line Home Insurance spokesman Simon Ziviani.

“Homeowners need to think extremely carefully before making changes to their properties, to ensure that they don’t end up costing them dearly.”

Ten design crimes to avoid

Alteration Average price reduction % have carried out/plan Cheap wooden flooring £3,854 33% Fitting UPVC windows £9,637 32% Fitting budget kitchen/bathroom £9,637 23% Removing period features £9,637 21% Removing fireplaces £3,854 20% Installing a fish pond £3,854 8% Dark coloured decoration £9,637 8% Knocking down room partitions £3,854 7% Concrete front garden £3,854 4% MDF partitions £3,854 2%