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Surface finishes rustic, sanded

Colours red, salmon, white

250/120 / 55 3,0

Kemano® hard-fired facing bricks (solid)

Designation L x W x H Weight

Quality to DIN 105 mm approx. kg

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Surface finishes rustic

Colours brick red, Sahara, Jura

Acoustic facing bricks

Designation L x W x H Weight mm approx. kg

Perforated side ground Colours: red, salmon, brown

For details of current products see www.swissbrick.com.

For details of a comparable selection of clay bricks and blocks as available on the

German market see www.ziegel.de (German Brickmaking Industry Association).

Masonry terminology

Systems

Fig. 32: Irregular or rustic bond

Fig. 33: Different types of course

Definitions excerpted from Wasmuths Lexikon der Baukunst, with borrowings from the Penguin Dictionary of Building and

British Standard 6100.

Clay masonry unit. A brick or block made from ioam or clay and hardened by means of firing. Available in various forms and sizes. See "Clay brick" below for more information.

Clay brick, clay block. A man-made building component made from clay, i oam or clayey substances - sometimes with the addition of sand, quartz fragments, dried clay dust or fired clay - dried in the air or fired in a kiln. If they are fired, we obtain the familiar clay brick commonly used in building. They are generally prismatic in shape but there are regional variations in the dimensions which have also changed over the course of time.

Hard-fired bricks. Clay bricks fired up to the point of sintering, and with a surface which is already lightly vitrified. Such bricks are used for facing masonry applications. One stretcher and one header face are fired to "facing quality".

Bed joint. A horizontal mortar j oint in brickwork or block-work. In arches and vaulting the bed joints run between the arching/vaulting courses.

Perpend. The vertical mortar j oint (1 cm wide on average) between bricks or blocks in the same course of brickwork or blockwork, which shows as an upright face joint. In arches and vaulting the perpends are the joints between the masonry units of one and the same course.

Stretcher. A brick, block or stone laid lengthwise in a wall to form part of a bond.

Header. A brick or block laid across a wall to bond together its two sides.

Course. A parallel layer of bricks or blocks, usually in a horizontal row of uniform format, including any mortar laid with them. Depending on the arrangement of the masonry units we distinguish between various types of course (see fig. 33).

Bonding dimension. In a masonry bond this is the dimension by which the masonry units in one course overlap those of the course below.

Bond. A regular arrangement of masonry units so that the vertical joints of one course do not coincide with those of the courses immediately above and below. To create a proper masonry bond, the length of a masonry unit must be equal to twice its width plus one perpend.

Masonry. A construction of stones, bricks or blocks. Wall. Generally, a building component constructed using stones, bricks, blocks or other materials with or without a bonding agent. Walls in which there is no mortar in the joints, merely moss, felt, lead, or similar, are known as dry walls.

Depending on height and function, we distinguish between foundation, plinth, storey and dwarf walls. These expressions are self-explanatory, as are the distinctions between enclosing or external walls, and internal walls or partitions. If walls support the loads of joists, beams, etc., they are known as loadbearing walls. If they have to withstand lateral pressures, they are known as retaining walls.

Fig. 33: Different types of course

Further reading

- Wasmuths Lexikon der Baukunst, Berlin, 1931

- Günter Pfeifer, Rolf Ramcke et al.: Masonry ConstructionManual, Basel/Boston/ Berlin, 2001.

- Fritz Schumacher: Das Wesen des neuzeitlichen Backstehbaues, Munich, 1985.

- Fleischinger/Becker: Die Mauer-Verbände, Hannover, 1993.

- Ludwig Debo: Lehrbuch der Mauerwerks-Konstruktionen, Hannover, 1901

- Plumridge/Meulenkamp: Ziegel in der Architektur, Stuttgart, 1996.

Design and construction b) v/v.y.

Fig. 34: Examples of jointing a) Bucket handle b) Flush c) Weathered

(non-facing side of masonry partially exposed to weather)

d) Recessed

(non-facing side of masonry partially exposed to weather)

e) Protruding

(joint material severely exposed to weather)

Masonry components

Masonry components comprise masonry units joined with mortar. The complete assembly then exhibits certain properties, which are discussed below.

Masonry bonds

Half- and one-brick walls

The thickness of the wall is equal to either the width of the masonry unit (half-brick wall) or its length (one-brick wall). The following terms describe the arrangement of the masonry units:

- stretcher bond - a half-brick wall with the masonry units laid lengthwise along the wall

- header bond - a one-brick wall with the masonry units laid across the wall

- header bond with brick-on-edge courses

Bonded masonry

The width of the thickness of the wall is greater than the length of one masonry unit. A great variety of masonry bonds can be produced through different combinations of stretcher and header courses. The dimension of such bonds are the result of the particular sizes of the masonry units and the joints. Building with masonry units involves working with a relatively small-format, industrially produced building material - the bricks and blocks - in conjunction with mortar to form a bonded, larger construction element. The masonry bond is characteristic of masonry construction, and critical to its strength. In order to create interlocking corners, intersections, and junctions, the bond must continue uninterrupted at such details. To achieve this, the ratio of length to width of the units was originally an even number. The length of a standard-format masonry unit is therefore twice its width.

Apart from decorative walls with no loadbearing functions, the courses are always built with their vertical joints offset so that successive courses overlap. This overlapping should be equal to about one-third of the height of the masonry unit. It is recommended to take the following bonding dimensions as an absolute minimum:

Half- and one-brick walls: min. 1/5 x length of unit (= 6 cm) in the longitudinal direction

Bonded masonry: min. 6 cm in the longitudinal direction, min. 4 cm transverse (theoretical)

For reasons of stability, single-leaf walls consisting of one vertical layer must be > 12 cm thick, but > 15 cm when using aerated concrete units. The load-carrying capacity of single-leaf walls, especially slender walls, is primarily limited by the risk of buckling.

Double-leaf walls consist of an inner and outer leaf, with possibly a layer of thermal insulation and/or air cavity in between. The inner, loadbearing leaf should be 12-15 cm thick, whereas the outer, weatherproof leaf should be > 12 cm thick.

Joints

We distinguish between bed joints and perpends - the horizontal and vertical layers of mortar that bind together the individual masonry units. Masonry can be regarded as a composite building material consisting of mortar and bricks, blocks, or stones. From the structural viewpoint, the perpends are much less significant than the bed joints because they do not contribute to resisting tension and compression stresses. In terms of strength and movements, the mortar joints behave somewhat differently to the masonry units and this leads to shear stresses developing between the units and the mortar. It is generally true to say that the joints (the mortar component) should be kept as thin or as small as possible. On the other hand, a certain joint thickness is necessary in order to compensate for the tolerances of the units themselves. Therefore, bed joints with normal mortar should be 8-12 mm thick.

As the wall is built, the mortar bulges out on both sides of the joints (especially the bed joints). This excess mate-

Perpends

Bed joints

Fig. 35: Joint definitions rial is normally struck off, which, however, is not always possible on the side facing away from the bricklayer when building a double-leaf wall. This can lead to the (already) narrow air cavity between the two leaves of masonry becoming obstructed or blocked altogether. To be on the safe side, bulging of 2-3 cm should be allowed for.

Depending on the desired appearance of the structure, the joints can be finished in different ways: flush, recessed, etc. (see fig. 34). In masonry that has to satisfy a demanding specification, e.g. special acoustic, seismic or architectural requirements, the mortar in the perpends is crucial to achieving the desired properties. On the other hand, masonry that does not have to satisfy any special demands can even be constructed with brick-to-brick perpends (i.e. no mortar in the vertical joints).

Dimensional coordination

Every structure, facing masonry in particular, should take account of dimensional coordination in order to rationalise the design and construction. This is understood to be a system of principal dimensions that can be combined to derive the individual dimensions of building components. The application of dimensional coordination results in components (walls, doors, windows, etc.) that are harmonised with each other in such a way that they can be assembled without having to cut the masonry units.

Systems

The nominal dimensions are even multiples of the basic module. They represent the coordinating dimensions for the design. Manufacturers subtract the j oint dimension from these to arrive at a work size for each component.

The design team must specify whether the masonry concerned is normal masonry left exposed (e.g. in a basement), a faced external wall, or internal facing masonry. The requirements placed on the surface finish of the bricks or blocks, the jointing, and the quality of workmanship increase accordingly.

Thickness of wall

The thickness of the masonry in a half- or one-brick wall corresponds to the width or length of the unit respectively, and thicker walls depend on the bricks/blocks used and the bond chosen.

Length of wall

A wall may be any length. Any necessary adjustments and sufficient interlocking within the masonry bond are achieved by cutting/sawing the bricks or blocks. Short sections of wall, columns, and piers should preferably be of such a size that whole bricks or blocks can be used. In facing masonry the dimensions must be chosen to suit the desired appearance of the masonry bond.

Factory-produced cut bricks (called bats) for adjusting wall lengths are available for facing masonry only. As a rule, the bricks or blocks are cut/sawn on site when the masonry is to be plastered or rendered subsequently, or to suit non-standard dimensions.

Height of wall

Clay bricks and blocks should not be cut within their height. Coordination between the courses and the overall height of the wall is therefore essential. Various make-up units (called tiles) are available, and by combining these any desired overall height can be achieved. However, it is advantageous to choose the height such that make-up units are reduced to a minimum, if possible to just one size. A change in the normal bed j oint thickness should normally be reserved for compensating for unevenness and tolerances.

Nominal dimensions

Single-leaf loadbearing walls must be > 12 cm thick, but > 15 cm when using aerated concrete units. In double-leaf walls the inner, loadbearing leaf should be 12-15 cm thick, whereas the outer, non-loadbearing leaf should be > 12 cm thick for reasons of stability. The stability of slender walls is primarily limited by the risk of buckling, i.e. transverse tensile stresses can no longer be resisted without a large compression load.

Masonry bonds

Fig. 36: Plan showing courses in English bond

Ludwig Mies van der Rohe: country house in brick (project), 1923

Fig. 36: Plan showing courses in English bond

Ludwig Mies van der Rohe: country house in brick (project), 1923

"Exposing the invisible"

A thourough understanding of the way that masonry works and the manner in which many historic buildings were assembled are intrinsic to our knowledge about the various types of masonry bond. This also forms the foundation for the design and arrangement of facing masonry structures.

According to the definition in Wasmuths Lexikon der Baukunst, a masonry bond is the "proper assembly (bonding) of natural or man-made stones" in order to guarantee the even distribution of the loads throughout the masonry body and an interlock between the individual masonry units in three dimensions.

To achieve proper bonding and interlocking at corners, terminations, and intersections, special arrangements of the respective bonds are necessary. These are governed by rules based on centuries of experience.

The principles of masonry bonds using English bond as an example This applies only to a bond consisting of man-made masonry units (i.e. clay, calcium silicate, concrete bricks, or blocks).

1. Exactly horizontal courses of masonry units are the prerequisite for a proper masonry bond.

2. Stretcher and header courses should alternate regularly on elevation.

3. There should be as many headers as possible in the core of every course.

4. There should be as many whole bricks or blocks as possible and only as many bats as necessary to produce the bond (3/4 bats at corners and ends to avoid continuous vertical joints).

5. As far as possible, the perpends in each course should continue straight through the full thickness of the masonry.

6. The perpends of two successive courses should be offset by 1/4 to 1/2 of the length of a masonry unit and should never coincide.

7. At the corners, intersections, and butt joints of masonry components the stretcher courses should always continue through uninterrupted, whereas the header courses can form a straight joint.

8. At an internal corner the perpends in successive courses must be offset.

Numerous variations can be produced according to the principles of masonry bonds, indeed as interesting derivations based on the following logic: the length of a masonry unit is equal to twice its width plus one perpend (e.g. 29 =14 +14 + 1).

Fig. 44: Stretcher bond

The principal or trainee bonds

We distinguish between half-, one-brick, and bonded masonry. In half- and one-brick walls the width of the courses is limited to one half or the whole length of a masonry unit respectively, whereas in bonded masonry the bond can extend over more than one brick or block within the depth of the wall.

Half- and one-brick walls

Stretcher bond (common bond) All courses consist exclusively of stretchers. Owing to the bonding dimension, which is normally half the length of a masonry unit, this bond results in masonry with good tensile and compressive strength. Stretcher bond is suitable for half-brick walls only. It is therefore employed for internal partitions, facing leaves and walls made from insulating bricks/blocks. The bonding dimension can vary, but must be at least 1/4 x length of masonry unit.

Header bond

As all courses consist exclusively of headers, this bond is primarily suited to one-brick walls. Successive courses are offset by 1/4 x length of masonry unit. This is a bond with a very high compressive strength which in the past was frequently used for foundations, too. Owing to the short bonding dimension, however, header bond is susceptible to diagonal cracking following the line of the joints.

Fig. 45: Header bond

Fig. 44: Stretcher bond

Fig. 45: Header bond

Bonded masonry

English bond

This bond, with its alternating courses of headers and stretchers, is very widespread. The perpends of all header courses line up, likewise those of all stretcher courses.

English cross bond (St Andrew's bond) In contrast to English bond, in English cross bond every second stretcher course is offset by half the length of a brick, which on elevation results in innumerable interlaced "crosses". This produces a regular stepwise sequence of joints which improves the bond and therefore improves the strength over English bond.

Fig. 46: English bond

Fig. 46: English bond

Fig. 47: English cross bond

Variations on English bond

Flemish bond

In Flemish bond stretchers and headers alternate in every course. The headers are always positioned centrally above the stretchers in the course below. It is also possible, in one-brick walls only, to omit the headers and thus create a honeycomb wall. Flemish bond has often been used for faced walls, i.e. walls with the core filled with various masonry units grouted solid with mortar, because the alternating headers in every course guarantee a good interlock with the filling.

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