Brickwork
Brickwork is masonry produced by a bricklayer, using bricks and mortar. Typically, rows of bricks called courses are laid on top of one another to build up a structure such as a brick wall.
Bricks may be differentiated from blocks by size. For example, in the UK a brick is defined as a unit having dimensions less than and a block is defined as a unit having one or more dimensions greater than the largest possible brick.
Brick is a popular medium for constructing buildings, and examples of brickwork are found through history as far back as the Bronze Age. The fired-brick faces of the ziggurat of ancient Dur-Kurigalzu in Iraq date from around 1400 BC, and the brick buildings of ancient Mohenjo-daro in modern day Pakistan were built around 2600 BC. Much older examples of brickwork made with dried bricks may be found in such ancient locations as Jericho in Palestine, Çatal Höyük in Anatolia, and Mehrgarh in Pakistan. These structures have survived from the Stone Age to the modern day.
Brick dimensions are expressed in construction or technical documents in two ways as co-ordinating dimensions and working dimensions.
- Coordination dimensions are the actual physical dimensions of the brick with the mortar required on one header face, one stretcher face and one bed.
- Working dimensions is the size of a manufactured brick. It is also called the nominal size of a brick.
An example of a co-ordinating metric commonly used for bricks in the UK is as follows:
- Bricks of dimensions 215 mm × 102.5 mm × 65 mm;
- Mortar beds and perpends of a uniform 10 mm.
There are many other brick sizes worldwide, and many of them use this same co-ordinating principle.
Terminology
As the most common bricks are rectangular prisms, six surfaces are named as follows:- Top and bottom surfaces are called beds
- Ends or narrow surfaces are called headers or header faces
- Sides or wider surfaces are called stretchers or stretcher faces
A brick made with just rectilinear dimensions is called a solid brick. Bricks might have a depression on both beds or on a single bed. The depression is called a frog, and the bricks are known as frogged bricks. Frogs can be deep or shallow but should never exceed 20% of the total volume of the brick. Cellular bricks have depressions exceeding 20% of the volume of the brick. Perforated bricks have holes through the brick from bed to bed, cutting it all the way. Most of the building standards and good construction practices recommend the volume of holes should not exceed 20% of the total volume of the brick.
Parts of brickwork include bricks, beds and perpends. The bed is the mortar upon which a brick is laid. A perpend is a vertical joint between any two bricks and is usually—but not always—filled with mortar.
A "face brick" is a higher-quality brick, designed for use in visible external surfaces in face-work, as opposed to a "filler brick" for internal parts of the wall, or where the surface is to be covered with stucco or a similar coating, or where the filler bricks will be concealed by other bricks.
Orientation
A brick is given a classification based on how it is laid, and how the exposed face is oriented relative to the face of the finished wall.; Stretcher or stretching brick: A brick laid flat with its long narrow side exposed.
; Header or heading brick: A brick laid flat with its width exposed.
; Soldier: A brick laid vertically with its long narrow side exposed.
; Sailor: A brick laid vertically with the broad face of the brick exposed.
; Rowlock: A brick laid on the long narrow side with the short end of the brick exposed.
; Shiner or rowlock stretcher: A brick laid on the long narrow side with the broad face of the brick exposed.
Cut
The practice of laying uncut full-sized bricks wherever possible gives brickwork its maximum possible strength. In the diagrams below, such uncut full-sized bricks are coloured as follows:;
;
Occasionally, however, a brick must be cut to fit a given space or to be the right shape for some purpose — for example, creating an offset at the beginning of a course. In some cases these special shapes or sizes are manufactured. In the diagrams below, some of the cuts most commonly used for generating a lap are coloured as follows:
; : A brick cut to three-quarters of its length, and laid flat with its long, narrow side exposed.
; : A brick cut to three-quarters of its length, and laid flat with its short side exposed.
; : A brick cut in half across its length, and laid flat.
; : A brick cut in half down its width, and laid with its smallest face exposed and standing vertically. A queen closer is often used for the purpose of creating a lap.
Less frequently used cuts are all coloured as follows:
; : A brick cut to a quarter of its length.
; : A queen closer cut to three-quarters of its length.
; : A brick with one corner cut away, leaving one header face at half its standard width.
Bonding
A nearly universal rule in brickwork is that perpends should not be contiguous across courses.Walls, running linearly and extending upwards, can be of varying depth or thickness. Typically, the bricks are laid also running linearly and extending upwards, forming wythes or leafs. It is as important as with the perpends to bond these leaves together. Historically, the dominant method for consolidating the leaves together was to lay bricks across them, rather than running linearly.
Brickwork observing either or both of these two conventions is described as being laid in one or another bond.
Thickness (and leaves)
A leaf is as thick as the width of one brick. A wall is said to be "one brick thick" if it is as wide as the length of a brick. Accordingly, a single-leaf wall is a half brick thickness; a wall with the simplest possible masonry transverse bond is said to be one brick thick, and so on.The thickness specified for a wall is determined by such factors as damp proofing considerations, whether or not the wall has a cavity, load-bearing requirements, expense, and the era during which the architect was or is working. Wall thickness specification has varied considerably, and while some non-load-bearing brick walls may be as little as half a brick thick, or even less when shiners are laid stretcher bond in partition walls, other brick walls are much thicker. The Monadnock Building in Chicago, for example, is a very tall masonry building, and has load-bearing brick walls nearly thick at the base. The majority of brick walls are however usually between one and three bricks thick. At these more modest wall thicknesses, distinct patterns have emerged allowing for a structurally sound layout of bricks internal to each particular specified thickness of wall.
Cavity walls and ties
The advent during the mid twentieth century of the cavity wall saw the popularisation and development of another method of strengthening brickwork—the wall tie. A cavity wall comprises two totally discrete walls, separated by an air gap, which serves both as barrier to moisture and heat. Typically the main loads taken by the foundations are carried there by the inner leaf, and the major functions of the external leaf are to protect the whole from weather, and to provide a fitting aesthetic finish.Despite there being no masonry connection between the leaves, their transverse rigidity still needs to be guaranteed. The device used to satisfy this need is the insertion at regular intervals of wall ties into the cavity wall's mortar beds.
Load-bearing bonds
Courses of mixed headers and stretchers
Flemish bond
has stretcher between headers, with the headers centred over the stretchers in the courses below.Where a course begins with a quoin stretcher, the course will ordinarily terminate with a quoin stretcher at the other end. The next course up will begin with a quoin header. For the course's second brick, a queen closer is laid, generating the lap of the bond. The third brick along is a stretcher, and is—on account of the lap—centred above the header below. This second course then resumes its paired run of stretcher and header, until the final pair is reached, whereupon a second and final queen closer is inserted as the penultimate brick, mirroring the arrangement at the beginning of the course, and duly closing the bond.
Some examples of Flemish bond incorporate stretchers of one colour and headers of another. This effect is commonly a product of treating the header face of the heading bricks while the bricks are being baked as part of the manufacturing process. Some of the header faces are exposed to wood smoke, generating a grey-blue colour, while other simply vitrified until they reach a deeper blue colour. Some headers have a glazed face, caused by using salt in the firing. Sometimes Staffordshire blue bricks are used for the heading bricks.
Brickwork that appears as Flemish bond from both the front and the rear is double Flemish bond, so called on account of the front and rear duplication of the pattern. If the wall is arranged such that the bricks at the rear do not have this pattern, then the brickwork is said to be single Flemish bond.
Flemish bond brickwork with a thickness of one brick is the repeating pattern of a stretcher laid immediately to the rear of the face stretcher, and then next along the course, a header. A lap is generated by a queen closer on every alternate course:
Double Flemish bond of one brick's thickness: overhead sections of alternate courses, and side elevation
The colour-coded plans highlight facing bricks in the east–west wall. An elevation for this east–west wall is shown to the right.
A simple way to add some width to the wall would be to add stretching bricks at the rear, making a Single Flemish bond one and a half bricks thick:
Overhead sections of alternate courses of single Flemish bond of one and a half bricks' thickness
The colour-coded plans highlight facing bricks in the east–west wall. An elevation for this east–west wall is shown to the right.
For a double Flemish bond of one and a half bricks' thickness, facing bricks and the bricks behind the facing bricks may be laid in groups of four bricks and a half-bat. The half-bat sits at the centre of the group and the four bricks are placed about the half-bat, in a square formation. These groups are laid next to each other for the length of a course, making brickwork one and a half bricks thick.
To preserve the bond, it is necessary to lay a three-quarter bat instead of a header following a quoin stretcher at the corner of the wall. This fact has no bearing on the appearance of the wall; the choice of brick appears to the spectator like any ordinary header:
Overhead plans of alternate courses of double Flemish bond of one and a half bricks' thickness
The colour-coded plans highlight facing bricks in the east–west wall. An elevation for this east–west wall is shown to the right.
For a more substantial wall, a header may be laid directly behind the face header, a further two headers laid at 90° behind the face stretcher, and then finally a stretcher laid to the rear of these two headers. This pattern generates brickwork a full two bricks thick:
Overhead sections of alternate courses of double Flemish bond of two bricks' thickness
The colour-coded plans highlight facing bricks in the east–west wall. An elevation for this east–west wall is shown to the right.
Overhead sections of alternate courses of double Flemish bond of two and a half bricks' thickness
The colour-coded plans highlight facing bricks in the east–west wall. An elevation for this east–west wall is shown to the right.
For a still more substantial wall, two headers may be laid directly behind the face header, a further two pairs of headers laid at 90° behind the face stretcher, and then finally a stretcher laid to the rear of these four headers. This pattern generates brickwork a full three bricks thick:
Overhead sections of alternate courses of double Flemish bond of three bricks' thickness
The colour-coded plans highlight facing bricks in the east–west wall. An elevation for this east–west wall is shown to the right.