GVA is 30% owned by Lloyds Development Capital, which increased its stake to give GVA an acquisition war chest 18 months ago. It has a turnover of around £6 million in Scotland, while Barr's has been static at around £4m for the past few years. The combined firm, to be known as GVA James Barr, will be in Scotland's top three behind international player Jones Lang Lasalle and the Edinburgh-based independent Ryden.
Eric Forgie, chief executive of James Barr and one of the 12 directors who owned the business, said: "It was clear we needed to upscale our operations to meet the increasing demand for our services in what has become a fiercely competitive marketplace for property consultancy and transactional advice.
"James Barr has traded profitably and remains debt-free, as it has done continually over its 140-year history."
Mr Forgie added: "This is genuinely driven by our strategic review, we either continued to paddle very fast in a very difficult market or make a more dramatic move - go out and acquire a Scottish business or merge into a much bigger game.
"We have always punched above our weight and we have got some very big global clients."
He said Barr had always been seen as an industrial property specialist but in fact it operated across all sectors, with offices in Glasgow and Edinburgh.
There was "not a great deal of overlap" with GVA in sectors or clients, and the new business would now be "much more visible".
Keith Aitken, head of GVA in Scotland, said: "The deal will offer both businesses the strength in depth required to compete pan sector throughout Scotland."
Rob Bould, chief executive of GVA, said: "James Barr has long been at the forefront of Scotland's property scene and maintains deep-rooted bonds with the Scottish corporate, private and public sectors.
"At this stage in the economic cycle, this is a first class acquisition of what is undoubtedly one of Scotland's leading surveyors."
He said GVA had increased profits substantially and was now "12 months away from becoming a debt-free business".