Costain : Scrip Dividend Reference Price

Costain Group PLC

('Costain' or the 'Company')

Scrip Dividend Reference Price

The Company announces that the Scrip Dividend Reference Price for the fully paid shares in the Company to be issued to shareholders who elect to receive the scrip dividend alternative for the interim dividend for the year ending 31 December 2017 is 437.0 pence per ordinary share of 50 pence each.

The Scrip Dividend Reference Price has been calculated in the usual way as the average of the middle market quotations for the Company's shares as derived from the Daily Official List of the London Stock Exchange for the five business days commencing on the ex-dividend date. The Company's ordinary shares were marked ex-dividend on 14 September 2017.

Further Information:

Shareholders wishing to receive the scrip dividend in respect of the interim dividend for the year ending 31 December 2017 and who have not already submitted a mandate form should return a mandate form to Equiniti Limited, Share Dividend Team, Aspect House, Spencer Road, Lancing, West Sussex BN99 6DA to arrive no later than 29 September 2017.

Mandate forms and the scrip dividend booklet containing the terms of the Company's scrip dividend scheme are set out on the Company's website at:

www.costain.com/investors/shareholder-centre/dividend-scrip/

If you have already completed a valid scrip dividend mandate form, it will remain valid until you cancel your election and you need not return any documentation to receive this scrip dividend.

The interim dividend for the year ending 31 December 2017, including the scrip dividend, will be paid on 20 October 2017 (the dividend payment date) to the ordinary shareholders of the Company on the register at close of business on 15 September 2017 (the record date).

For further information, please contact Equiniti on 0371 384 2270*.

21 September 2017

*Lines are open 8.30am to 5.30pm, Monday to Friday, excluding bank holidays. If you are calling from outside the UK please telephone +44(0)121 415 7047.