Mortar Fillet

To complete the weathering, the projecting brickwork or creasing tiles must be provided with a sloping finish to shed rainwater. This is achieved with a mortar fillet (see Fig 207), which should be a flat, sloping surface of between 35 and 45 degrees.

To ensure that the top edge of the fillet runs to an even, straight line, attaching a string-line is much quicker and more accurate than trying to do it by eye.

Mortar Fillet

Fig. 230 String-line used as a guide for the top of a mortar fillet.

Mortar Fillet

Fig. 231 Mortar fillet ‘roughed-in’ to the string-line.

Load the brick trowel blade with mortar and, using the back of a pointing trowel, scrape mortar from the brick trowel and ‘rough-in’ the fillet to the line. Use the pointing trowel in a downward

motion from the line, using the edge of the oversailing course (or tile creasing) to ‘clean’ the back of the pointing trowel. Try to keep the diagonal, downward movement of the pointing trowel as straight as possible, to achieve a flat surface to the sloping fillet. It is very easy to end up with a convex curve to the fillet unless care is taken at these early stages.

Mortar Fillet

Fig. 232 Mortar fillet polished and compacted with a wet pointing trowel.

Remove the string-line and, if required, apply small amounts of mortar with the pointing trowel to fill in any obvious dips or hollows in the fillet. Leave the mortar to go off, as is the practice prior to jointing-up brickwork. Then, using the back of a pointing trowel, polish and compact the surface of the fillet by drawing the trowel along the length of the fillet. This process is vital to ensure a smooth finish and the weather resistance of the mortar fillet and is greatly assisted by keeping the pointing trowel wet. Have a bucket of water to hand for this purpose.

Mortar Fillet

Fig. 233 Finished mortar fillet.