Total Voting Rights and Capital

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

Total Voting Rights and Capital

In conformity with the Financial Conduct Authority's ("FCA") Disclosure Guidance and Transparency Rule 5.6.1(R) the Company notifies the market that:

As at 30 April 2019, the Company's issued share capital comprises 107,677,792 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 in order to satisfy the exercise by employees of their options under the Company's Long Term Incentive Plan and allotments of shares to employees who participate in the Company's employee Sharesave Plan.

The figure of 107,677,792 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 Costain, or a change to their interest in Costain, under the FCA's Disclosure Guidance and Transparency Rules.

1 May 2019

Enquiries:

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