The buildings were generally built with double wall dry-stone walls packed with earth and wooden rafters covered with a thatch of turf with cereal straw or reed. The floor was generally flagstones or packed earth and there was a central hearth for the fire. There was no chimney for the smoke to escape through. Instead the smoke made its way through the roof. This led to the soot blackening of the interior which may also have contributed to the adoption of name blackhouse.
The blackhouse was used to accommodate livestock as well as people. People lived at one end and the animals lived at the other with a partition between them.