This diagram illustrates the structure of an early iron age hut or roundhouse. As we can see from the diagram, the hut had a very simple construction composed of a central column supporting a conical roof. The roof is composed of reed thatch, layered over rafters. The floor of the hut would be excavated slightly lower than ground level and a low turf wall was erected around the perimeter of the structure. A small fire could be lit in the centre of the space to provide warmth. No chimney was required as smoke could freely escape through gaps in the thatch roof. I think this picture is very educational and informative