Environmental consultant RSK Group has bought building envelope and testing specialist Building Sciences.

Building Services turned over £405,000 in the year to 31 August 2007 and its sale price is estimated to be in this region.

The deal for the 20-strong Oxfordshire firm cements RSK’s position as the UK’s largest privately owned environmental consultancy. RSK has 750 staff in 36 offices throughout the world with a turnover of £41.6m.

It has bought six companies since January 2007 and has six deals in the pipeline. It hopes to boost turnover to £100m by 2011 and staff levels to 1,100.

Alan Ryder, the group chairman, said: “Legislation and consumers are demanding greater efficiency in design and RSK and Building Sciences want to make that a reality.”