Bricks have been used for building since earliest times, alone or in combination with stone, timber, concrete or otrher building materials. They are a very logical answer to a series of requirements for a building material.
Bricks evolved in size and weight to suit the human hand – one hand picking up the brick while the other hand lays the mortar bed. It’s even possible that smaller, weaker builders have used lighter, smaller and easier to grip bricks than stronger bricklayers. It’s been said that the standard London clay brick size of 215mm x 102.5mm x 65mm (8 1/2″ x 4″ x 2 1/2″) was enlarged over a few generations by Britain’s strapping Australian cousins to a new local standard of 230mm x 110mm x 76mm (9″ x 4 1/2″ x 3″). A bigger brick means faster construction. Even in Australia, however, the ‘metric’ or ‘modular’ brick of 290mm x 90mnm x 90mm (300mm x 100mm x 100mm with 10mm mortar joints) has failed to catch on. It’s just too big and heavy. Note that a 230mm length of a standard brick is also the thickness of a solid (non-cavity) wall comprising two ‘leaves’ of standard bricks 110mm wide with a 10mm mortar joint between the leaves. The length of a modular brick is greater than the width of a solid, two-leaved wall of modular bricks.
Bricks are easy to produce in quantity and can be made of most soils with a clay content. These bricks are usually fired to produce a hard, ceramic product capable of bearing great loads. If no clay, or lime – or kiln – is available, bricks may be made literally of mud, perhaps reinforced with straw, then air dried. These bricks, known as adobe, are individually fragile, and weather easily, but laid en masse and protected from the rain by a render or overhangs, they can last for thousands of years. Bricks may also be made with cement as a binder. Cement sets chemically and makes for a very strong brick.
Bricks are usually laid with mortar joints. The ‘frog’ or depression in older bricks and to an extent the holes in modern clay bricks accept mortar and allow some lateral mechanical grip, desirable especially with lime mortar which is weak in shear compared with later cement mortars.
Building bricks are laid in numerous patterns according to purpose and appearance. These patterns are called ‘bonds’. The simplest is ‘stretcher bond’ in which bricks are laid flat and longwise, with the next layer or ‘course’ staggered half a brick to prevent vertical joints, called ‘perps’ for perpendicular, occurring exactly above each other and weakening the structure.
Bricklaying is an ancient and noble art, with a language of its own. A brick laid flat is a stretcher. A brick laid across a double leafed wall, as described above, is a ‘header’. A half brick is a ‘bat’ (hence ‘brickbat’) and amusingly a brick ‘standing up’ with the narrowest 76mm edge facing is a ‘soldier’ while a standing brick presenting its wider 110mm side to the eye is a ‘sailor’. Various shaped bricks such as those moulded with bevels etc are called ‘specials’, of which there are many – cants, bullnoses, closers, queen closers etc.
Bricks are a simple, economical and efficient building material – cheap to make, easy to transport and easy to lay. Their limitations as are similar to those of natural stone. Increased loads, usually due to building height, require increased thickness of lower walls; fire weakens brickwork, often due to the different behaviour in extreme heat of bricks and the mortar between them; and earthquakes tend to displace or crack brickwork, which lacks the flexibility of steel beams or to a lesser extent, steel reinforced concrete.
Nevertheless, the humble brick endures, and should be treated with respect. Bricks continue to do their job well, thousands of years after the first one was laid.