The deal sees private equity firm LDC achieve a partial exit, but leaves Palatine and LDC with a combined majority stake in the business.
Forrest is a leading provider of refurbishment and responsive maintenance services to the social housing market in the North of England.
The business also undertakes new build development and estate renewal services for its core social housing customer base.
Forrest has seen its turnover grow from £38m in 2007 to over £100m and now employs around 500 people.
Bob Holt, chairman of social housing company Mears Group, will become non-executive chairman while current chairman Robert Morgan will leave the business.
Lee McCarren, Chief Executive Officer at Forrest, said: “LDC, led by Jonathan Bell, have been a hugely supportive partner for the business over the past six years.
“With Palatine alongside us as an additional investor, we can continue to drive improvements in the quality of our customer service offering, as well as developing more new and complementary service lines.
“On behalf of the business, I’d like to thank Robert for his invaluable counsel and for the time and energy which he has invested into Forrest since he became our chairman. He has played an influential role in the company’s recent successes.”