It is understood that the purchase of the 15-strong Midlands office is a precursor to a much larger acquisition - a move predicted by the AJ in November ( Capita plans two architectural acquisitions 'by Christmas').
Established in 2001, Church Lukas' Birmingham-based office's projects include student residences for the University of Nottingham and the Dysart Road Retail Park in Grantham.
Work is also about to start on site for the South Lynn Millennium Village in Norfolk, a Millennium Community project.
As a result of the takeover, Church Lukas director Gary Church has been appointed to head the Birmingham office.
Rob Firth, CPT's head of architecture said: 'We are delighted to welcome Church Lukas and their Birmingham staff to Capita Percy Thomas.
'Birmingham is a key area of expansion for us and the experience and reputation of such a well-established practice in the area will be a major asset for us going forward.'
Meanwhile, Church Lukas' Nottingham office, which is not part of the deal, will continue to operate under the name it has worked under since it was founded in 1993.