One-brick walls built in stretcher bond have an inherent weakness due to the continuous vertical ‘collar joint’ that runs the full height of the wall between the front half-brick thickness and the back half-thickness. Whilst this can be overcome by using short cavity-wall ties, stretcher bond is arguably best avoided for one-brick thick boundary walls. English and Flemish bonds are much stronger alternatives.
For attached piers to be effective, they must be bonded or tied into the main wall, be at least 100mm thick and, as a minimum, terminate within a height measured from the top of the wall equal to three times the wall’s least thickness. For example, a pier attached to a one-brick wall (215mm thick) must terminate no lower than 645mm from the top of the wall.
More detail on finishing off the tops of boundary walls and piers is given later in this chapter.
Since such piers are defined as being attached to the main wall, it follows that the main wall should be bonded first and then the projecting pier tied or bonded into it. This should be done in the course
that is most convenient while at the same time trying to adhere to the basic principles of bonding. When working out how best to tie in a pier to the main wall, particular attention should be given to the arrangement of bricks to ensure continuity of the transverse joints through both wall and pier, and to reduce cutting to a minimum.