The earliest remains of housing in Ireland were found at Mount Sandel in Co. Derry, which is located on a height about 30 metres overlooking the river Bann, a few miles from the sea. The site was excavated between 1973 and 1977 by Peter Woodman. He got radio-carbon dates of c.7010 bc to c. 6490 bc. In levels of excavation dating 500 years he found the remains of a number of round houses roughly 6 metres in diameter, which are the oldest Mesolithic houses to be found in Ireland and they predate anything found in Britain.
The remains that could be seen were in the form of post-holes – rounded stains left over from wood that had decayed. The post holes were about 20 cm deep were at an angle going inwards. This suggests that the houses were in a dome shape, made of saplings bent inwards and joining towards the centre, there was no central support pole. A hearth of roughly a metre in diameter would have been located in the centre of the house. The outer posts of wood would probably have had lighter saplings weaved around them forming a shelter, possibly covered over with more mud and sticks (wattle and daub) or sods of earth.
The location of Mount Sandel would have been ideal for Mesolithic Man, as they were close to the sea, and fresh-water streams for fishing and could find game in the woods nearby. This may be why there are traces of such long habitation in this area. Also there was a source of flint along the Antrim Coast which provided the settlers with raw material for their tools and weapons. In general Mesolithic Man was a hunter-gatherer and would probably have been nomadic living in temporary shelters, which is why there is not much evidence of housing from this time period.
source: Museum of Learning