Sanaas new areas were physically different than the quarters of the old city. Many of the Yemenis who had migrated to the Gulf states had worked in construction, where they had become well-acquainted with Western and Egyptian techniques. When they returned to Yemen, they brought those techniques with them. New construction consisted of concrete and concrete block houses, with multi-lite windows and plaster decorations, laid out in a grid pattern. Their amenities, including independence from extended families and the possibility of owning a car, attracted many families from the old city, and they moved to the new districts in growing numbers. Meanwhile, the old city, with its unpaved streets, poor drainage, lack of water and sewer systems, and litter (from use of manufactured products, which was becoming increasingly common), was becoming increasingly unattractive to residents. Disaster struck in the late 1970s — water pipes were laid to bring water into the old city, but there was no way to pipe it out, resulting in huge amounts of groundwater building up in the old city. This destabilized building foundations and led to many houses collapsing.