Conversation so far:
When did the Gaelic Ireland settlements begin?
Square and rectangle-shaped buildings gradually became more common, and by the 14th or 15th century they had replaced round buildings completely.
What did they replaced the Gaelic Ireland round buildings with?
Square and rectangle-shaped buildings gradually became more common, and by the 14th or 15th century they had replaced round buildings completely.
Who did the Gaelic Ireland architecture designs?
After the invasion, the Normans built motte-and-bailey castles in the areas they occupied, some of which were converted from ringforts
Did Gaelic Ireland residents move from a different place before the settlements?
Yes, most date to the period 500–1000 CE and there is evidence of large-scale ringfort desertion at the end of the first millennium.

Question: Around what time did they change the architect?
Self-contained rewrite: Around what time did Gaelic Ireland residents change the architect?