Engineering brick
Engineering bricks are a type of brick used where strength, low water porosity or acid (flue gas) resistance are needed. Engineering bricks can be used for damp-proof courses.
Clay engineering bricks are defined in British Standard BS 6100 "Glossary of building and civil engineering terms" as "brick sized fired clay units having a dense and strong semi vitreous body, conforming to defined limits for water absorption and compressive strength."[1]
Stronger and less porous engineering bricks (UK Class A) are usually blue due to the higher firing temperature[2] whilst class B bricks are usually red. Class A bricks have a strength of 125N/mm² and water absorption of less than 4.5%; Class B bricks have a strength greater than 75N/mm² and water absorption of less than 7%.
Accrington brick is one type of engineering brick.