Kilwaughter Minerals, the Larne-based quarrying group, has bought an English firm, Alumasc Facades, for £4.5m.
Kilwaughter operates a 75-acre limestone quarry and makes products used in construction, agriculture and industry.
Alumasc Facades makes a range of construction renders and external wall insulation systems.
Kilwaughter said the deal will expand its product offering in construction markets across the UK and Ireland.
'Major growth opportunity'
Managing Director Simon McDowell said: "The acquisition will provide us with a major growth opportunity to develop the business with our greater operational scale, access to raw materials and expertise in manufacturing."
It will pay up to a further £1.5m in one year's time, based on the performance of the business during that period.
Kilwaughter now employs around 200 people across two manufacturing sites with six distribution facilities.
Last years its holding company made a pre-tax profit of £9.6m on turnover of £33m.