Directorate Change

COSTAIN GROUP PLC

("Costain" or the "Company")

Retirement of non-executive director/change in senior independent director

Costain has today announced that, as part of its planned Board succession, James Morley will retire as a non-executive of the Company, and as senior independent director, with effect from the conclusion of Costain's Annual General Meeting to be held on Tuesday 8 May 2018 (the "2018 AGM").

At a Board meeting held on 26 February 2018, Jane Lodge was appointed to act as the Company's senior independent director with effect from the conclusion of the 2018 AGM. The appointment of a senior independent director reflects good corporate governance and meets the requirements of Provision A.4.1 of the UK Corporate Governance Code.

James Morley joined the Board in January 2008 and was chairman of the Company's audit committee until October 2012 and was appointed as senior independent director in January 2013.

Jane first joined the Board as an independent non-executive director in August 2012 and was appointed chair of the audit committee with effect from the end of October 2012. She is also a member of the Company's remuneration and nomination committees. She is currently also a non-executive director and chair of the audit committee at Devro PLC, DCC plc and Sirius Minerals plc. She is also a non-executive director of the Bromsgrove School Foundation.

Dr Paul Golby CBE, chairman, said: "I would like to thank James Morley for more than 10 years of dedicated service to Costain, during which time he has made a very significant contribution. I wish him well for the future. I am also delighted that Jane Lodge, a highly experienced director, will be succeeding James as the Company's senior independent director. Jane will bring valuable knowledge, experience and insight to this important role".

This information has been disclosed pursuant to LR 9.6.11.

 26 February 2018