Engineering bricks have high compressive strength and low water absorption properties. They are rated as either class A or B, with A being the strongest and they are ideal for use below ground level and for Damp proof courses.
Common bricks have low compressive strength and are of lower quality than engineering or facing bricks as no attempt is made to control their colour or appearance. They should not be used below ground and are generally used for internal brickwork only. The term "frogged common" is sometimes used as a generic term for "flettons" or LBC faced commons. These are bricks that have a common coloured base and then have different face colours added.
Facing bricks give a building its aesthetic appearance and are designed to be used externally against internal block work or brickwork to provide an attractive 'face'. They are by far the most popular type of brick and come in a huge variety of colours and sizes.