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Special bricks

Clay bricks allow the architect a tremendous palette of colours along with a variety of textured finishes, all of which offer an unlimited range of design features.

In addition to the aesthetic qualities of fired clay, bricks may also be manufactured in a multitude of special shapes. In quality projects, 'specials', as they are referred to, can often be used to enhance the appearance of corners, edges and openings in the finished brickwork.

Rounded and chamfered edges provide the typical profiles which may be incorporated into the header or stretcher lengths of bricks. With these simple modifications to the standard brick, we have available an infinite choice of design features.

Special-shaped bricks provide two particular advantages when incorporated into a building design. Firstly, they help the architect to achieve any desired effect in terms of the building lines and profile.

Secondly, special shaped bricks provide a functional role both in helping to enhance good detailing practice and in simplifying the construction of brickwork. In some cases one can fabricate clay units which help to make the bricklaying process simpler, for example the use of angled corners or the availability of quarter, half and three-quarter units. In other cases, specials help to produce the good detailing which is so essential to the production of a weather-proof structure that must stand for many decades, for example copings and sill bricks.

Standard specials are detailed in BS4729 and each shape has a standard code that allows simple specification procedures. Within the standard range, specials are grouped into categories depending on their main functions. For example, those in the first group are known as 'bonding bricks'. These help to simplify the bricklaying process by reducing the number of cut bricks needed to produce a wall, eg quarters, halves, and three-quarter units. Larger blocks, such as stop ends, are available to finish off wall capping and coping details. Other groups include the units necessary to produce angled and radial brickwork as well as the rounded and chamfered edged units that enhance details to corners and openings.

The dimensions of standard specials have been calculated carefully to ensure there is a minimal amount of cutting and that simple bonding is achievable.

The other category of specials is the non-standard group. In essence, this category allows a manufacturer to produce any special shaped unit that might be required to achieve a certain architectural feature. Generally the design-services department will advise on the necessity for non-standard specials as it may be that the required detail can be achieved with standard units. Naturally, the standard shapes are usually simpler to manufacture and are more readily available. However, for those elaborate or prestigious brickwork details which might require units not covered by the British Standard, the purpose-made specials may provide the perfect solution.

The extent to which special-shaped bricks are incorporated into a building design is entirely dependent on the designer's objectives.

Quite often a minimal use of units - such as a plinth stretcher detail at the base of a building - may be all that is necessary to give a desired outline to the structure. Alternatively, some buildings make a dominant feature detail which requires a major input of special shapes. In some cases this might amount to 20 per cent of the entire brick quantity. The choice will be that of the designer, perhaps with some practical advice from the brick manufacturer.

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