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."