Block Listing Application

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

Block Listing Application

The Company announces that applications have been made to the UK Listing Authority and to the London Stock Exchange for the admission of a total of 718,218 Ordinary Shares of 50p each in the capital of the Company (the "Shares") to the Official List and to trading on the main market for listed securities by way of a Block Listing.

The Shares will be issued pursuant to the exercise of share options under the Company's employee Sharesave Plan and will, upon issue, rank pari passu in all respects with the Company's existing issued Ordinary Shares. Admission of these Shares is expected to become effective on Thursday 01 November 2018.

29 October 2018