On stretcher bond walls that do not work to a half a brick length and for most other bonds, reverse bond is not an option so an alternative solution must be found. One possibility is to either widen or narrow the thickness of all the cross-joints throughout the length of the wall, to ‘gain’ or ‘lose’ the desired amount that means the wall length will then ‘work bricks’, whether to full – or half-brick length. The accepted tolerance for adjusting the width of cross-joints is
10mm + or-3mm; strictly speaking, this tolerance actually exists to allow for the slight variation in the sizes of individual bricks.
Fig. 100 Examples of broken bond.
This course of action presents a number of problems. First, adjusting the width of cross-joints is generally not an option on short walls as the small number of cross-joints limits the scope for significantly adjusting the wall length. Second, wider cross-joints can look particularly unsightly, even when staying within the acceptable tolerance of +3mm, and applying a joint finish tends to make joints look wider still. On this basis, if cross-joints need to be adjusted then narrowing them is arguably the lesser of two evils. Third, the width of cross-joints must be consistent and the verticality of cross-joints throughout the height of the wall must not ‘wander’ unacceptably. The process of adjusting the width of cross-joints away from the usual 10mm tends to lead to a lack of consistency in width and ‘wandering’ cross-joints will inevitably appear, particularly on long walls.
dry bond the wall first, and then to take a view on whether the proposed adjustment is aesthetically acceptable. Where it is not acceptable, it becomes necessary to introduce cuts into the middle of straight walling. This is known as a ‘broken bond’.
Broken bonds must visually and structurally maintain the integrity of the original bond. The smaller the cuts, the more noticeable they become, so the accepted bonding rule is that cuts no smaller than a half-brick should be introduced into the middle of a wall. This will maintain a minimum overlap of a quarter-brick. If it is any less, the structural capabilities of the wall in terms of load distribution will be impaired.
Maintaining the verticality of perpends or cross-joints has already been identified as an important factor in bricklaying generally, but extra care must be taken where the positioning of broken bonds is concerned. Excessive vertical deviation of cross-joints will draw undesirable attention to the broken bond.
When cutting bricks for a broken bond, they must be cut accurately and neatly (a fair-faced cut), and all cuts must be the same size. To this end, it is common for all the bricks required for a broken bond to be measured, marked and cut first in one batch. This is also a more efficient way of working, as the bricklayer does not have to stop on every course to cut bricks.
There will always be a few alternative ways of broken bonding to suit a specific situation and the bricklayer must find the most appropriate solution in each case. This is achieved by attempting to balance a number of factors: using cuts that are as big as possible so that the broken bond is not too noticeable; using as few cuts as possible on each course, so as to minimize the amount of time spent cutting; and, finally, ensuring that the original bond is not compromised aesthetically or structurally. This can be achieved only by dry bonding the centre portion of the walling, in order to test the various solutions available.
Fig. 101 Broken bond at openings.
On buildings, any broken bonds should be set-out so that they are centred above and below any openings. This avoids any unsightly small cuts being placed either side of an opening at the reveals, helps to minimize the extent to which the broken bond is visible, and reduces the amount of cutting. The position of window and door reveals should be set-out with full stretchers on the first course of brickwork at finished ground level, which are then plumbed up the face of the wall as it is built in order to accurately position the frames at their required height. Fig 101 shows, in red, the position of the openings set-out in full stretchers at ground level and how these positions are transferred vertically to the reveals. There is a broken bond placed centrally under the window opening.