How much would a £42,000 extension put onto the value of a house?

House extensions can add up to 25 per cent to the value of your home, depending on the build cost, size and type of extension.

So, spending £42,000 on an extension will add a different amount to the value of your home depending on your property’s existing size, its current value and the type of extension you have undertaken.

For example, adding a £42,000 extension to a terraced property valued at £75,000 is unlikely to add anywhere near the same value to your home. This is because the extension is likely to be disproportionate to the size and value of the house. As Channel 4 says, ‘...if your four-bedroom property is in a street of two and three-bedroom houses, extending it to make it five or even six-bedroom could make it difficult to get the return.’

However, a £42,000 extension to a property valued at £250,000 which adds extra bedroom and reception rooms may well add more than the build cost to the property value. Channel 4 reports that ‘an extension could add between 10 and 50 per cent to the value of your home, depending on its size and how well it's finished.’ But, if you are planning on spending £42,000 or more on an extension, make sure you undertake the right type of extension.

Douglas Sleaper, of Townends estate agents told the Independent in 2011, “extensions that add key living space, such as bedrooms, kitchens and dining areas, are the most valuable. This is particularly true of making a three-bedroom property into a four-bedroom, as it really increases the number of potential buyers. But there's a diminishing return in terms of pounds per square foot by extending – the sixth bedroom won't be worth as much as the third, for example.”

Research by Savills has also shown that the price of a four-bedroom home is, on average, 71 per cent more than a three-bedroom property. So, if you are planning to extend your home, make sure you keep to your budget and undertake sensible, proportionate building work.

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