He said it would allow Wolseley to develop its North American business.
Wolseley, which is based in Worcestershire, generates 60% of its income from North America and has applied for a listing on the New York Stock Exchange.
Westburn, which has 19% of the Canadian plumbing, refrigeration and industrial supplies market, also operates in the USA.
Westburn employs 3000 people and has 19% of the Canadian plumbing, refrigeration and industrial supplies market
Wolseley said Westburn would be integrated into its US businesses. The one-off costs of the integration are expected to be £7m.
Westburn recorded pre-tax profit of £39m last year, on turnover of £650m. It has 3000 staff.
Wolseley's share price rose 3.5p to 532.5p after the announcement, with analysts generally positive about the deal.