Non-facing Plastered

NFP : Non Facing Plastered - Clay bricks suitable for general building work that is to be plastered

Non-facing Extra

NFX : Non Facing Extra - Clay bricks suitable for use, plastered or unplastered, for general building work below damp-proof course or under damp conditions or below ground level where durability rather than aesthetics is the criterion for selection

Engineering Units

E : Engineering Units - Any class masonry unit produced for structural or load-bearing purposes in face or non-face work, where the manufacturer supplies clay bricks to an agreed compressive strength. An engineering unit is designated by the addition of the letter E followed by a number equal to the nominal compressive strength in megapascals, e.g. FBSE21