Laying the Last Brick to Line
The last brick in a course of brickwork can be awkward to lay, whether it is to a line or not. Cross-joints should be applied to both ends of the last brick but the brick should not be pushed straight down vertically into the gap, as this can cause the cross-joint mortar to be scraped off by the bricks either side. Instead, the brick is reversed in and down at an angle, the cross-joint is squeezed up and then the front end is lowered down (see Fig 141).
Fig. 141 Laying the last brick to a line. FACE-PLANE DEVIATION
Following running-in, be it to a spirit level on a small job or a string-line on a large job, it is necessary to check the deviation of the face plane of the wall. This involves placing a straight-edge on the face of the wall and across both diagonals in order to check the flatness of the finished brickwork (see Fig 142). On short walls this can often be achieved with the edge of the spirit level.
Checking the face-plane deviation is not only a measure of how well the brickwork has been run-in but also a measure of how well the two ends or corners of the wall were originally constructed. Any error in the construction of the ends or corners will be transferred to, and replicated in, the middle section of the wall when it is run-in! The accepted tolerance for face-plane deviation is no more than 5mm in any 3m length.
Despite their size (six times bigger than bricks), the craft operations in erecting walls and corners from blocks are much the same as for bricks, with a couple of exceptions. The vertical height and face area of a typical block greatly exceeds its width and bedding face area, so, when laying blocks for the first course of a corner, they should never be levelled across their width. Instead, they should only be levelled along their length and plumbed vertically up their face. The latter, assuming the faces of the blocks are square (which they usually are), will provide more than adequate provision for level across their width. This principle applies to a lesser degree where much wider blocks are used, but reference is made here to blocks that are 100mm wide.
When running-in the first course of a block wall, the large height of blocks and the lack of a lower reference point to which to align the bottom edge make it quite easy for blocks to end up leaning over one way or the other. To avoid this it
is common either to line in the bottom edge of the first course
with a long straight-edge between the corners (see Fig 143), or, if the wall is too long, to attach a second string-line as close to the bottom edge as possible in order to create a lower reference point to which to align the faces of the blocks.
Fig. 143 Building block walls and lining in the first course with a straight-edge.
A good flat face-plane block for blockwork walling is vital – one block that is out of vertical alignment is much more noticeable than one misaligned brick, because of its size. That said, an accurate face plane still depends upon adopting exactly the same principles as when laying bricks to a line (see Fig 143). Block B must be laid with its top edge parallel to the line (as close as possible to the line without touching it) and its lower edge flush with the top edge of block A.