Total Voting Rights

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

Total Voting Rights and Capital

In accordance with the Financial Conduct Authority's ("FCA") Disclosure and Transparency Rule 5.6.1(R), this is to confirm that, as at the date of this notice, the Company's issued share capital comprises 66,654,220 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 the exercise of share options under the Company's employee savings related share option scheme.

The figure of 66,654,220 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.

30 August 2013

Enquiries:

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