Constructing Isolated Piers
When building the pier, it is fundamentally important for it to be vertically upright (‘plumb’) and for all four sides to be square with one another. The key to achieving the latter begins with the first course, which will dictate everything that happens on subsequent courses. The example (see Fig 206) is a 2-brick by 1^-brick pier in stretcher bond; following the correct sequence of operations will ensure that it is constructed square and plumb:
1. Start by laying the front two stretchers to gauge, level, in line and to the correct length, in this case, 440mm (Stage 1).
2. Construct the two sides by squaring the side bricks from the front bricks, which are known to be in line (Stages 2 and 3).
3. Check that each of the two new sides measures 327mm (Stage 4).
4. The back brick can be simply ‘run-in’ to the ends of the side bricks by using the spirit level as a straight-edge.
5. As a final check, measure from corner to corner across both diagonals, which, if the first course is square, should be equal (Stage 5). A centre in-fill brick can be laid, if required, on each course.
Subsequent courses begin with the corner brick at the gauging point (‘G’) from which the remaining three corner bricks are levelled. When laid, each corner brick must be plumbed on both sides to ensure it is vertical and not twisting as it gains height, meaning that the pier has a total of eight plumbing points (‘P’). After all the corner bricks have been positioned, the side bricks can be run-in for line
and level to the corner bricks by using the spirit level as a straight-edge. Again, and on every course, check the diagonals to make sure the pier remains square.
When building piers of any type, attached or isolated, it is necessary to be selective about the bricks that are being used. The comparatively small size of a pier, the relatively small number of cross-joints and the need for great accuracy means that tolerances become quite tight. Any bricks that are oversized, undersized and/or misshapen should be discarded in favour of more consistently sized and shaped examples.
Sometimes, to save bricks, mortar and time, piers are constructed hollow. This is achieved by omitting the centre in-fill bricks and/or by reducing the length of bricks so that what remains is a hollow core surrounded by a half-brick skin. In some cases where the pier is not required for structural support, the void is left empty, but in other cases, where structural strength is required, the void is filled with wet concrete, sometimes supplemented with steel reinforcement. As wet concrete exerts a lateral pressure on the insides of the pier, sufficient time should be allowed for the mortar to harden before pouring the concrete.