Loft and roof conversions were found to be the most popular renovations planned, along with the construction of a conservatory or extension.
Neil Laird, home insurance manager for Sainsbury's Finance, said the findings emphasises the importance of buildings insurance.
He said: "We want to make sure that homeowners are aware that they could be left underinsured or even invalidate their insurance entirely in the event of an incident during or after the works if they have not informed their insurer first."
Previous research by Sainsbury's Home Insurance found that around 4.7 million adults in the UK do not have home contents insurance.
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