ANDREA DEPLAZES (ED.)                    BIRKHÄUSER
             CONSTRUCTING ARCHITECTURE
               MATERIALS PROCESSES STRUCTURES 
             A HANDBOOK
                              Materials-Modules
                                     Msonry
                       1-3 Design and Construction
                Birkhäuser – Publishers for Architecture
                Basel · Boston · Berlin
                                                                      MAMATERIALS – MODULESTERIALS – MODULES                           MasonrMasonryy
                                                                                                                                                                                                                         Systems
                                                                      Design and construction
                                                                                                                                       Masonry components                                                                                    Joints
                                                                                                                                       Masonry components comprise  masonry units joined with                                                We distinguish between bed joints and perpends – the 
                                                                                                                                       mortar. The complete assembly then exhibits certain pro-                                              horizontal and vertical layers of mortar that bind together 
                                                                                                                                       perties, which are discussed below.                                                                   the individual  masonry units. Masonry can be regarded 
                                                                                                                                                                                                                                             as a composite building material consisting of mortar and 
                                                                                                                                       Masonry bonds                                                                                         bricks, blocks, or stones. From the structural viewpoint, 
                                                                                                                                       Half- and one-brick walls                                                                             the perpends are much less significant than the bed joints 
                                                                                                                                       The thickness of the wall is equal to either the width of                                             because they do not contribute to resisting tension and 
                                                                                                                                       the   masonry unit ( half-brick wall) or its length ( one-brick                                        compression stresses. In terms of strength and move-
                                                                                                                                       wall). The following terms describe the arrangement of                                                ments, the mortar joints behave somewhat differently to 
                                                                                                                                       the  masonry units:                                                                                   the  masonry units and this leads to  shear stresses de-
                                                                                                                                       -  stretcher bond – a  half-brick wall with the  masonry                                              veloping between the units and the mortar. It is generally 
                                                                                                                                             units laid lengthwise along the wall                                                            true to say that the joints (the mortar component) should 
                                                                                                                                       -     header bond – a             one-brick wall with the  masonry units                              be kept as thin or as small as possible. On the other hand, 
                                                                                                                                             laid across the wall                                                                            a certain  joint thickness is necessary in order to compen-
                                                                                                                                       -      header bond with brick-on-edge courses                                                         sate for the tolerances of the units themselves. Therefore, 
                                                                                                                                                                                                                                             bed joints with normal mortar should be 8–12 mm thick.
                                                                                                                                       Bonded  masonry                                                                                             As the wall is built, the mortar bulges out on both sides 
                                                                                                                                       The width of the thickness of the wall is greater than the                                            of the joints (especially the bed joints). This excess mate-
                                                                                                                                       length of one  masonr                y unit. A great variety of  masonry 
                                                                                                                                       bonds can be produced through different combinations 
                                                                      a)                                                               of stretcher and  header courses. The dimension of such                                                                                                                         Perpends
                                                                                                                                       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 pro-
                                                                                                                                       duced building material – the bricks and blocks – in con-                                                                                                                        Bed joints
                                                                                                                                       junction with mortar to form a bonded, larger construction 
                                                                                                                                       element. The  masonr                y bond is characteristic of  masonry                              Fig. 35: Joint definitions
                                                                      b)                                                               construction, and critical to its strength. In order to create                                        rial is normally struck off, which, however, is not always 
                                                                                                                                       interlocking corners, intersections, and junctions, the bond                                          possible on the side facing away from the bricklayer when 
                                                                                                                                       must continue uninterrupted at such details. To achieve                                               building a  double-leaf wall. This can lead to the (already) 
                                                                                                                                       this, the ratio of length to width of the units was originally                                        narrow  air cavity between the two leaves of  masonry 
                                                                                                                                       an even number. The length of a standard-format   masonry                                             becoming obstructed or blocked altogether. To be on the 
                                                                                                                                       unit is therefore twice its width.                                                                    safe side, bulging of 2–3 cm should be allowed for.
                                                                      c)                                                                     Apart from decorative walls with no loadbearing func-                                                 Depending on the desired appearance of the struc-
                                                                                                                                       tions, the courses are always built with their vertical joints                                        ture, the joints can be finished in different ways: flush, 
                                                                                                                                       offset so that successive courses overlap. This overlap-                                              recessed, etc. (see fig. 34). In  masonry that has to satisfy 
                                                                                                                                       ping should be equal to about one-third of the height of                                              a demanding specification, e.g. special acoustic, seismic 
                                                                                                                                       the   masonry unit. It is recommended to take the following                                           or architectural requirements, the mortar in the perpends 
                                                                                                                                       bonding dimensions as an absolute minimum:                                                            is crucial to achieving the desired properties. On the other 
                                                                      d)                                                                     Half- and one-brick walls: min. 1/5 x length of unit                                            hand,  masonry that does not have to satisfy any special 
                                                                                                                                       (= 6 cm) in the longitudinal direction                                                                demands can even be constructed with brick-to-brick 
                                                                                                                                             Bonded  masonry: min. 6 cm in the longitudinal direc-                                           perpends (i.e. no mortar in the vertical joints).
                                                                                                                                       tion, min. 4 cm transverse (theoretical)
                                                                                                                                             For reasons of stability, single-leaf walls consisting of                                        Dimensional  coordination
                                                                                                                                       one vertical layer must be * 12 cm thick, but * 15 cm                                                 Every structure,  facing  masonry in particular, should take 
                                                                      e)                                                               when using aerated concrete units. The load-carrying                                                  account of dimensional coordination in order to rationalise 
                                                                      Fig. 34: Examples of  jointing                                   capacity of single-leaf walls, especially slender walls, is                                           the design and construction. This is understood to be a 
                                                                      a) Bucket handle                                                 primarily limited by the risk of  buckling.                                                           system of principal dimensions that can be combined to 
                                                                      b) Flush
                                                                      c) Weathered                                                           Double-leaf walls consist of an inner and outer leaf,                                           derive the individual dimensions of building components. 
                                                                      (non-facing side of  masonry partially exposed to                with possibly a layer of thermal  insulation and/or air                                               The application of dimensional coordination results in 
                                                                      weather)
                                                                      d) Recessed                                                      cavity in between. The inner, loadbearing leaf should be                                              components (walls, doors, windows, etc.) that are har-
                                                                      (non-facing side of  masonry partially exposed to 
                                                                      weather)                                                         12–15 cm thick, whereas the outer, weatherproof leaf                                                  monised with each other in such a way that they can 
                                                                      e) Protruding                                                    should be * 12 cm thick.                                                                              be assembled without having to cut the  masonry units. 
                                                                      ( joint material severely exposed to weather)
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                                                                                                                                                                        MAMATERIALS – MODULESTERIALS – MODULES                                                                               MasonrMasonryy
                                                                                                                                                                                                                 Systems
                                                                                                        The nominal dimensions are even multiples of the basic 
                                                                                                        module. They represent the coordinating dimensions for 
                                                                                                        the design. Manufacturers subtract the  joint 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  base-
                                                                                                        ment), 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 workman-
                                                                                                        ship 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 
                                                                                                        masonr       y 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  joint 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 sta-
                                                                                                        bility 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.
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