High-value homeowners are being urged not to attempt artificial reductions to their property valuations after last week’s Budget introduced a new annual tax on homes worth more than £2 million.

The caution follows an analysis by London estate agent Benham and Reeves, which examined the extent to which cosmetic deterioration or loss of kerb appeal can affect buyers’ perceptions of value.

Although the exercise was framed as a light-hearted look at “reverse renovations”, it highlights how sensitive high-end valuations can be to relatively small visual changes.

According to the firm’s estimates, minor alterations such as opting for an unpopular front-door colour could reduce a £2 million valuation by around 0.8%, or £16,000.

POOR MAINTENANCE

More substantial detractors – including installing artificial grass or removing a driveway –  could in theory trim between 5- and 7% from perceived value, equating to £100,000 to £140,000.

Poor maintenance carries an even greater impact. An abandoned car on the drive was assessed as shaving roughly 7%, or £140,000, from a £2 million home’s perceived worth, while a neglected garage could erode value by about 7.5%.

An untidy garden, one of the clearest indicators of disrepair to prospective buyers, was estimated to knock as much as 8% (£160,000) off a valuation.

Unpainted brown pebbledash (main picture) ranked among the most serious cosmetic deterrents, with a putative 10% effect, or £200,000.

Severe visual blight, such as decaying water features or derelict swimming pools, could depress perceived value by 10.7%, according to the analysis, while parking a caravan prominently in the front garden could reduce it by 12%.

LOOKS MATTER

Marc von Grundherr (main picture, inset), director of Benham and Reeves, said the Budget had “sharpened the focus of homeowners whose properties sit around the £2m mark”, prompting the firm’s exploration of how far exterior appearance can influence valuations.

But he emphasised that any attempt to manipulate a property’s value would be inadvisable and potentially counterproductive.

He said: “What this exercise does show, however, is how sensitive the market can be to cosmetic condition. If anything, it reinforces the importance of good presentation when selling, regardless of what the tax landscape might look like.”