General term applied to roughly circular houses typical of the later 2nd and 1st millennia bc in northwest Europe, especially the British Isles. Such houses may be of timber construction or have stone foundations with a timber superstructure. In general the doorways open in a southeasterly direction and they have central hearths. Those which functioned as dwellings would have been home to an extended family. Although the timber superstructures and thatched roofs are often regarded as a fire hazard, experiments show that these buildings can have a long life and that, with a fire burning inside, a layer of carbon dioxide gas builds up under the roof and serves to extinguish any stray sparks rising up towards the thatch. See stone hut circle.