Conversation so far:
What type of settlements were there in Gaelic Ireland?
There were very few nucleated settlements, but after the 5th century some monasteries became the heart of small monastic towns.
What did the buildings in Gaelic Ireland look like?
For most of the Gaelic period, dwellings and farm buildings were circular with conical thatched roofs.

Question: What material were the buildings made of?
Self-contained rewrite: What material were the buildings in Gaelic Ireland made of?