By James Brinsford A Grand Designs project, which was described as “lunacy” by the Channel 4 show’s presenter Kevin McCloud, has suffered £200,000 worth of damage after it was claimed a builder forgot one of the most important rules. Richard Hawkes, 49, and wife Sophie, 50, built their “gravity defying” dream home near Maidstone, Kent but the arch that showcases the building was unsupported and constituted of Plaster of Paris and tiles, which were 100mm thick. The method is usually reserved for domed structures and the were allegedly told not to lean on it during construction of what was a wor…