Spreading Bed Joints
Having achieved a trowel full of mortar, the next stage is the spreading of a bed joint, followed by furrowing ready to receive bricks. Bed joints must not be spread too thickly as too much effort will be required to tap the brick down to gauge (a 10mm bed joint). Ideally, a bed joint should be spread sufficiently thinly so the brick can be pressed to gauge with little or no tapping from the trowel.
At this point the bricklayer should not turn round so that the trowel hand is over the wall, but bring the trowel hand across the body, and then proceed as follows:
1. Hold the trowel of mortar over the position where the bed joint is required. This may be the surface of a concrete foundation at the start of new work or on top of the previous course of brickwork for work that is ongoing.
2. Spreading involves transferring a trowelful of mortar into something resembling a line of mortar. Turn the trowel vertically through 90 degrees and combine a dropping motion with, simultaneously, sweeping or drawing the trowel blade backwards along and parallel to the line of brickwork. In general terms, the direction of spreading is always along the wall and not across it, regardless of whether headers or stretchers are being laid.
Fig. 111 Spreading mortar.
3. If the mortar bed has not quite spread evenly, pick up thicker parts with the trowel edge and deposit them at one end of the line of mortar so that the initial spreading is more even and elongated.
Fig. 112 Elongating the initial spread of mortar.
4. With the point of the trowel, ‘furrow’ the spread mortar along its length and backwards with a series of undulating trowel movements. This creates an indentation along the spread mortar, which, when a brick is pressed into it, fills to form a full bed joint. It avoids too much mortar being squeezed out of the joint, which could fall down the face of the brickwork below and cause staining. Full joints are vital, and furrowing the mortar too deeply can result in voids in the bed joints, which will affect the structural strength of the finished brickwork.
Fig. 113 Furrowing mortar.
5. Having furrowed the mortar, use the inside edge of the trowel with the top face of the blade turned outwards to trim off any mortar that overhangs front and back in order to provide a neat edge to the bed joint in readiness to receive bricks.
When spreading bed joints for cavity walling it is very important not to let the mortar bed overhang on the cavity side. Great care should be taken to prevent mortar falling down the cavity, which could result in the cavity becoming bridged and lead to water ingress through the finished wall. The mortar that is trimmed off should not be allowed to fall or be deposited on the floor. Instead, efficient, practical use
should be made of it by placing it at one end of the line of mortar so that the initial spreading is further elongated.