The new addition to the MGM Timber line-up, which has operated for 69 years, will enable MGM Timber to improve its customer offering in the surrounding area, in addition to its existing branches in Glasgow, Wishaw and Ayrshire.
Robert Reid & Sons Ltd will continue to trade under its existing name. All existing staff will be retained.
The announcement follows the news that MGM Timber is to expand nationally, with the firm on the hunt for premises in Edinburgh and Aberdeen.
The firm, which started trading in 1991, has grown to employ 160 members of staff across 12 sites and has a turnover of £41.68m.
David Mansell, managing director for MGM Timber, said: "We already have a number of established and well performing sites across Scotland and the addition of Robert Reid & Sons Ltd will enable us to suitably service customers in the West of Scotland to help meet consumer demand.
"We are looking forward to developing and growing Robert Reid & Sons and ensuring that it remains the local merchant of choice for the town."