Some of the houses on Malé are built in imitation of those in Colombo. Most residential units throughout the country have brick walls, some of which are also plastered, and roofs of galvanized metal sheets. The poorest homes are made from thatch and sticks. According to a 2000 housing census, there were about 43,556 residential units nationwide. About 96% were detached dwellings. About 325 were apartments. The average dwelling size is from three to six rooms. About 48% of all dwellings had been built from 1990–2000. Nearly 68% of the population relies on rain water as a primary source of water; 43% of all dwellings have septic tanks. About 84% of households have electric lighting, but firewood and oil are the primary heating and cooking fuels.