Total Voting Rights

Costain Group PLC("Costain" or the "Company")

Total Voting Rights and Capital

In conformity with the Financial Conduct Authority's ("FCA") Disclosure and Transparency Rule 5.6.1(R) we would like to notify the market of the following:

As at the date of this notice, the Company's issued share capital comprises 105,592,847 ordinary shares of 50 pence each, with each share carrying the right to one vote. The Company does not hold any ordinary shares in treasury.

The increase in the number of issued shares has arisen due to an allotment of shares to employees who participate in the Company's employee Sharesave Plan.

The figure of 105,592,847 shares may be used by shareholders as the denominator for the calculations by which they will determine if they are required to notify their interest in, or a change to their interest in, Costain under the FCA's Disclosure and Transparency Rules.

28 February 2018

Enquiries:

Costain Group PLC Tel: 01628 842444Tracey Wood, Company Secretary