NFU Mutual adds a 55% loading on to thatched homes. But Norwich Union Home Plan is a lot more expensive. It would charge £1,210 a year for building insurance for a threebedroom thatched cottage in the picturesque village of Lavenham in Suffolk, with a rebuilding cost of £250,000.A similar house with a tiled roof would cost £403 - two-thirds less.ut Norwich Union Home Plan is a lot more expensive. It would charge £1,210 a year for building insurance for a threebedroom thatched cottage in the picturesque village of Lavenham in Suffolk, with a rebuilding cost of £250,000.