Conversation so far:
What type of settlements were there?
There were very few nucleated settlements in Gaelic areas.
What did the buildings look like?
It was at this time, perhaps as a response to Viking raids, that many of the Irish round towers were built.
What material were the buildings made of?
concentrated in counties Limerick and Clare but are lacking in Ulster, except the area around Strangford Lough.
Did the buildings survive?
surrounded by a wall (see bawn) and ancillary buildings.
Gaelic families had begun to build their own tower houses by the 15th century.
What else did they build during this time period?
".
The Normans gradually replaced wooden motte-and-baileys with stone castles and tower houses.
What other materials did they use to build?
while sitting at his house, could cast a cnairsech (variously described as a spear or sledgehammer.
Is there anything else interesting?
Ordnance Survey Ireland.
Another kind of native dwelling was the crannog, which were roundhouses built on artificial islands in lakes.
What other types of housing did they use?
some areas, buildings were made mostly of stone.
In others, they were built of timber, wattle and daub, or a mix of materials.
Did many people like these settlements?
Among the wealthy, it was common for women to have their own 'apartment' called a grianan (anglicized "greenan") in the sunniest part of the homestead.

Question: How were they able to make the settlements so durable?
Self-contained rewrite: How were the people in Gaelic Ireland able to make the settlements so durable?