Departing chief Martin, 53, denied the shake-up was triggered by Trian and said it was a “coincidence”.
“We have had the demerger of the UK on the agenda for a long time. It won’t come as any surprise for shareholders, it’s coincidence of timing,” he said.
“The succession follows that. When the main business is totally focused on America it is appropriate for the business to be managed by someone focused in north America.”
One Ferguson shareholder said the company was responding faster to Trian’s overtures than expected and they were surprised Martin was standing down after only three years.
Martin said it was the right thing to do. Wolseley UK will be led by current managing director Mark Higson.