What is the difference between facing, common and engineering bricks?

Brick classification runs on two axes at once, which is why the terminology is confusing. One axis is what the brick is for — facing, common or engineering. The other is how it was made — handmade, soft mud moulded, wirecut or pressed — which determines its texture, its face and its price. Both matter, and a merchant's product name usually tells you the first and not the second.

Step by step

1. Start from where the brick is going.Above ground and visible: facing. Below ground, in a manhole, or in a retaining situation: engineering, or a facing brick specifically rated for it. Hidden behind render or plaster: common.
2. Check the frost resistance rating, not the name."Facing brick" does not by itself mean frost resistant. Bricks carry an F rating for freeze-thaw durability, and that is what tells you whether it can go in an exposed position, a parapet or a garden wall.
3. Understand what a frog is and which way up it goes.The indentation in the bed face of a moulded or pressed brick. Frogs go upwards and are filled with mortar, which increases the bond and the strength of the wall. Laid frog down they leave a void and a weaker joint.
4. Know that perforated bricks are not weaker.The holes through a wirecut brick reduce weight and improve firing, and the mortar keys into them. They are structurally fine. What they do mean is that the brick cannot be cut anywhere and still look right, and it is unsuitable where a bed face will be exposed.
5. Do not use engineering brick above ground on an old wall.It is nearly impermeable, so water arriving at it goes into the softer brick and mortar around it instead. A course of engineering brick let into a soft Victorian wall concentrates decay on its neighbours.
6. Match by size as well as by colour.Metric standard is 215 x 102.5 x 65mm. Older buildings frequently use imperial sizes that are close but not identical, and metric bricks in an imperial wall will not gauge with the existing courses.
7. Buy the whole job in one batch.Brick colour varies between production runs. Order the full quantity plus wastage in one delivery, and mix bricks from several packs as you lay so that any variation is distributed rather than concentrated in one patch.

Alternatives

• Facing brick: Made to be seen. Consistent size, a presentable face, and a specified durability. Most of what is sold for house building and garden walls. Comes in an enormous range of colours and textures, and the range is regional.
• Common brick: A general-purpose brick with no particular attention to appearance. Cheaper. Used where the work will be rendered, plastered, buried or hidden. Many commons have poor frost resistance and should not be used exposed.
• Engineering brick: Very dense, high strength, very low water absorption, classified as Class A or Class B. Used below ground, in manholes and inspection chambers, as a damp proof course in some construction, and where strength or impermeability is needed. Class A is stronger and less absorbent than Class B.
• Wirecut: Extruded as a continuous column and cut with wires. Sharp arrises, very consistent, often with perforations through the brick. The commonest modern facing brick and the cheapest to make.
• Soft mud / stock: Clay thrown into moulds, giving a creased face and a frog — the indentation on one bed face. The traditional London stock and its equivalents. More variation, softer appearance, generally more expensive.
• Handmade: Individually thrown into sanded moulds. Irregular in size and shape, with a distinctive folded face. Used on restoration, conservation and high-end work, and priced accordingly.
• Pressed: Formed under pressure in a mould, giving a smooth, dense, precise brick with a deep frog. Includes many Victorian and Edwardian bricks and modern reproductions of them.

Questions people ask