Dutch contractor BAM has sold subsidiary Mostert De Winter to fellow Dutch contractor Elkarij.
Mostert De Winter specialises in roof gardens, faÃ§ade vegetation systems and landscaping.
The transaction includes all 39 employees, work in progress, plants and equipment.
BAM said it sees "insufficient opportunities for further development of the activities of Mostert De Winter" and that it "considers the added value of this specialization for the Group limited".
BAM, which has struggled with its results in recent years, said the sale is in line with its "Back in Shape" streamlining programme.
In 2014 Mostert De Winter had an estimated turnover of $18m. They will continue activities under their own name.
Elkarij has a turnover of approximately $220m and employs 2,200 people. Elkarij hopes to gain a prominent position in the market for green roofs and faÃ§ade.