IS Code for fly ash bricks is IS 13757 (1993): Burnt clay fly ash building bricks-Specification
For Modular Size
Length is 190± 4mm
Width is 90±2 mm
Height is 90±2 mm and 40±2 mm
For Non-Modular Size
Length is 230± 4mm
Width is 110±2 mm
Height is 70±2 mm and 30±2 mm