The purpose of buildings insurance is to cover you for any damage to the actual structure or fittings in your home. If you are trying to arrange this type of cover it should be for enough to cover the total rebuilding cost of your property. This means it should be around the cost of the property’s value if it were for sale, rather than the actual market value.
Most insurance companies will use a set formula to help you calculate the total re-building cost. Some properties such as a listed building or a more valuable property may require you to get a professional valuation carried out.
It is also worth remembering that the cost of the policy will go up each year as a result of inflation. You also may want to review the policy every 3 years or so to ensure you are insured for the right value.
It is also worth shopping around for buildings insurance. Your mortgage lender will probably offer you this with the mortgage; however it is often cheaper to get it elsewhere.