ROK has bought John Dickie Construction from the Scottish-based John Dickie Group for £750,000.
Dickie Construction will now be integrated with Rok's existing operations in Glasgow.
Dickie turned over £25 million in the year to March 2003. In the year to March 2004 the firm made a pre-tax profit of £1.39 million.
Rok chief executive Garvis Snook said: 'Dickie Construction's combination with Rok creates a major player in Scotland.'
John Dickie Group chairman Dermott Simpson said: 'The sale is an important step in our strategic goal of focusing on residential properties.'