 Complete the following phrase:  The house has a two-post Zweiständer design, whereby the posts, which support the usually-thatched roof half-hipped roof, are near to the outer walls. From the late 18th century the roof in the living area has been carried on the supporting outer walls. This variation, however, was only used in areas that were protected by strong dykes and was not adopted by Uthland-Frisian houses which occurred in regions endangered by storm surges. Even if the walls and the ground floor of such a post-and-beam house are destroyed by flooding, there is a very high probability that the upper storey will survive, so that the occupants of the house can take refuge on the roof. Ever since the serious 