Boral chairman Kathryn Fagg is under pressure from two shareholder activists to release the details of a deal between the board and Boral's largest shareholder, Seven Group Holdings.

This week Fagg received a letter signed by John Wylie from Tanarra Capital and Paul Skamvougeras at Perpetual Investments demanding the release of the full terms of the agreement that led to the appointment of two Seven Group representatives to the Boral board in September.