The move follows a spate of contract wins in England and Harvey Group now has plans to boost staff numbers by more than a third.
Operations Director Herbie Watterson, said: “Over the past number of years we have won substantial business outside Northern Ireland and our new office which will initially accommodate up to 15 staff has been opened with a view to increasing our employment numbers beyond our current Group figure of 110 to around 150.
“In the past couple of years we have invested around £2m across the business and our GB expansion will bring the total invested to around £4m by 2018.”
Harvey Group currently has a turnover of £30m and a £20m order book so far for 2016/2017 including Luton Airport, a CAT A Office Fit-out in Fenchurch Street, (NHS) Healthcare works and Lynchill Academy in Reading.