• Bricks bonding blocks

    Blocks are made in various thicknesses to suit most wall requirements and are laid in stretcher bond.

    Thin blocks, used for non-loadbearing partitions, are laid in running stretcher bond with each block centred over and under blocks above and below. At return angles full blocks bond into the return wall in every other course, as illustrated in Fig. 62. So as not to disturb the full width bonding of blocks at angles, for the sake of stability, a short length of cut block is used as closer and infill block.

    Thicker blocks are laid in off centre running bond with a three quarter length block at stop ends and sides of openings. The off centre bond is acceptable with thicker blocks as it avoids the use of cut blocks to complete the bond at angles, as illustrated in Fig. 62.
    Bonding building blocks
    Thick blocks, whose length is twice their width, are laid in running (stretcher) bond as illustrated in Fig. 62, and cut blocks are only necessary to complete the bond at stop ends and sides of opening.
    At the ‘T’ junctions of loadbearing concrete block walls it is sometimes considered good practice to butt the end face of the intersecting walls with a continuous vertical joint to accommodate shrinkage movements and to minimise cracking of plaster finishes.

    Where one intersecting wall serves as a buttress to the other, the butt joint should be reinforced by building in split end wall ties at each horizontal joint across the butt joint to bond the walls. Similarly, non-loadbearing block walls should be butt jointed at intersections and the joint reinforced with strips of expanded metal bedded in horizontal joints across the butt joint.

    Concrete block walls of specially produced blocks to be used as a fairface finish are bonded at angles to return walls with specially produced quoin blocks for the sake of appearance, as illustrated in Fig. 63. The ‘L’ shaped quoin blocks are made to continue the stretcher bond around the angle into the return walls.

    Bonding block walls

  • Bricks Clay blocks

    Hollow clay building blocks are made for use as a wall unit. The blocks are made from selected brick clays that are press moulded and burnt. These hard, dense blocks are hollow to reduce shrinkage during firing and reduce their weight and they are grooved to provide a key for plaster, as illustrated in Fig. 61. The standard block is 290 long x 215mm high and 62.5, 75, 100 and 150mm thick.

    Clay blocks are comparatively lightweight, do not suffer moisture movement, have good resistance to damage by fire and poor thermal insulating properties. These blocks are mainly used for non-load-bearing partitions in this country. They are extensively used in southern Europe as infill panel walls to framed buildings where the tradition is to render the external face of buildings on which the blocks provide a substantial mechanical key for rendering and do not suffer moisture movement that would otherwise cause shrinkage cracking.

    clay blocks

  • Concrete blocks moisture movement

    As water dries out from precast concrete blocks shrinkage that occurs, particularly with lightweight blocks, may cause serious cracking of plaster and rendering applied to the surface of a wall built with them. Obviously the wetter the blocks the more they will shrink. It is essential that these blocks be protected on building sites from saturation by rain both when they are stacked on site before use and whilst walls are being built. Clay bricks are small and suffer very little drying shrinkage and therefore do not need to be protected from saturation by rain. Only the edges of these blocks should be wetted to increase their adhesion to mortar when the blocks are being laid.

  • Bricks for building blocks

    Building blocks are wall units, larger in size than a brick, that can be handled by one man. Building blocks are made of concrete or clay.

    Concrete blocks

  • Bricks for Garden wall bonds

    Walls, such as garden walls, that are to be finished fairface both sides and built 1 B thick are often built in one of the garden wall bonds.
    Because of the variations in size and shape of many facing bricks it is difficult to finish a 1 B wall fairface both sides because of the differences in length of bricks that are bonded through the thickness of the wall.
    Garden wall bonds are designed specifically to reduce the number of through headers to minimise the labour in selecting bricks of roughly the same length for use as headers.

    Usual garden wall bonds are three courses of stretchers to every one course of headers in English garden wall bond and one header to every three stretchers in Flemish garden wall bond, as illustrated in Fig. 59.
    The reduction in the number of through headers does to an extent weaken the through bond of the brickwork. This is of little consequence in a freestanding garden wall. Other combinations such as two or four stretchers to one header may be used.
    garden wall bonds

  • Bricks bonding at angles and jambs

    At the end of a wall at a stop end, at an angle or quoin and at jambs of openings the bonding of bricks has to be finished up to a vertical angle. To complete the bond a brick ± B wide has to be used to close or complete the bond of the \ B overlap of face brickwork.

    A brick, cut in half along its length, is used to close the bond at an angle. This cut brick is termed a ‘queen closer’, illustrated in Fig. 56. If the narrow width queen closer were laid at the angle, it might be displaced during bricklaying. To avoid this possibility the closer is laid next to a header, as illustrated in Fig. 57. The rule is that a closer is laid next to a quoin (corner) header.

    There is often an appreciable difference in the length of facing bricks so that a solid wall 1 B thick may be difficult to finish as a wall fairface both sides. The word fairface describes a brick wall finished with a reasonably flat and level face for the sake of appearance. Where a 1 B wall is built with bricks of uneven length it may be necessary to select bricks of much the same length as headers and use longer bricks as stretchers. This additional care and labour will add appreciably to costs.

    Bricks bonding1
    Walls 1/(1/2) B thick may be used for substantial walling for larger buildings, such as industrial, storage and civic, for the sake of the appearance of the brickwork and the durability and sense of solidity and permanence where the walling is finished fairface both sides.
    To complete the bond of a solid wall 1/(1/2) B thick in double Flemish bond, that is Flemish bond on both faces, it is necessary to use cut half bricks in the thickness of the wall as illustrated in Fig. 57. At angles and stop ends of wall, queen closers are laid next to quoin headers and a three quarter length cut brick is used, as illustrated in Fig. 57.
    Bricks bonding2

    Cutting the many half length bricks (1/(1/2) bats) and three quarter length bricks and closers is time consuming and wasteful as it is not always possible to cut a brick in half cleanly. This adds considerably to the cost of this walling, which is selected for appearance rather than economy.
    1/(1/2)B thick wall, finished fairface both sides and showing English bond both sides, requires considerably less cutting of bricks to complete the bond, as illustrated in Fig. 58.It is only necessary to cut closers and three quarter length bricks to complete the bond at angles and stop ends.

    Walls 1/(1/2)B thick that are to be finished fairface on one side only may be built with facing bricks for the fairface side and cheaper common bricks for the rest of the thickness of the wall, where the inside face is to be covered with plaster.

  • Bonding Bricks

    In building a wall it is usual to lay bricks in regular, horizontal courses
    so that each brick bears on two bricks below. The bricks are said to be bonded as they bind together by being laid across each other along the length of the wall, as illustrated in Fig. 50.
    Bricks pyramid

    The advantage of bonding is that the wall acts as a whole so that the load of a beam carried by the topmost brick in Fig. 50 is spread to the two bricks below it, then to the three below that and so on down to the base or foundation course of bricks.

    The failure of one poor quality brick such as ‘A in a wall and a slight settlement under part of the foundation such as ‘B’ and ‘C in Fig. 50 will not affect the strength and stability of the whole wall as the load carried by the weak brick and the two foundation bricks is transferred to the adjacent bricks.

    Because of the bond, window and door openings may be formed in a wall, the load of the wall above the opening being transferred to the brickwork each side of the openings by an arch or lintel.
    The effect of bonding is to stiffen a wall along its length and also to some small extent against lateral pressure, such as wind.

  • Properties of bricks

    This is a somewhat vague term commonly used in the description of
    bricks. By general agreement it is recognised that a brick which is to have a moderately good compressive strength, reasonable resistance to saturation by rainwater and sufficient resistance to the disruptive action of frost should be hard burned. Without some experience in the handling, and of the behaviour, of bricks in general it is very difficult to determine whether or not a particular brick is hard burned.

    A method of testing for hardness is to hold the brick in one hand and give it a light tap with a hammer. The sound caused by the blow should be a dull ringing tone and not a dull thud. Obviously different types of brick will, when tapped, give off different sorts of sound and a brick that gives off a dull sound when struck may possibly be hard burned.

    Bricks Compressive strength
    Bricks Absorption
    Frost resistance of bricks
    Efflorescence of bricks
    Sulphate attack on mortars and renderings of bricks

  • Sulphate attack on mortars and renderings of bricks

    When brickwork is persistently wet, as in foundations, retaining walls, parapets and chimneys, sulphates in bricks and mortar may in
    time crystallise and expand and cause mortar and renderings to disintegrate. To minimise this effect bricks with a low sulphate content should be used.

  • Efflorescence of bricks

    Clay bricks contain soluble salts that migrate, in solution in water, to
    the surface of brickwork as water evaporates to outside air. These salts will collect on the face of brickwork as an efflorescence (flowering) of white crystals that appear in irregular, unsightly patches. This efflorescence of white salts is most pronounced in parapet walls, chimneys and below dpcs where brickwork is most liable to saturation. The concentration of salts depends on the soluble salt content of the bricks and the degree and persistence of saturation of brickwork.

    The efflorescence of white salts on the surface is generally merely unsightly and causes no damage. In time these salts may be washed from surfaces by rain. Heavy concentration of salts can cause spalling and powdering of the surface of bricks, particularly those with smooth faces, such as Flettons. This effect is sometimes described as crypto efflorescence. The salts trapped behind the smooth face of bricks expand when wetted by rain and cause the face of the bricks to crumble and disintegrate.

    Efflorescence may also be caused by absorption of soluble salts from a cement rich mortar or from the ground, that appear on the face of brickwork that might not otherwise be subject to efflorescence. Some impermeable coating between concrete and brick can prevent this. There is no way of preventing the absorption of soluble salts from the ground by brickwork below the horizontal dpc level, although the effect can be reduced considerably by the use of dense bricks below the dpc.