Mortar Joints in Exposed Masonry

Mortar joints are the filled spaces between the bricks, stones, or concrete blocks that make up a wall. Should you drill directly into the brick or into the surrounding mortar? And does it make a difference if a joint is not flush? (A flush mortar joint is one where the surface is smoothed out equal to the brick.) These, and more, points are addressed below.

Into the brick or into the joint?

For optimal strength and support, anchors for cable trellises are mounted in the brick/stone. Only in exceptional cases, and also if there are reservations against drilling into the stone, is fixing done in the mortar joints. Joint attachment is, however, often favoured.

Strength of mortar joints

Theoretically, in contemporary masonry, mortar joints are just as strong as the bricks they are binding. The joints of older buildings are generally less stable. Historically, concrete was a precious commodity and a diluted mortar was often used, which is highly prone to weather erosion and weakening over time. Behind a hard intact outer layer, joints can often be weak and brittle. If this is the case, you can secure your rawlplug or rawlplug free anchor using composite mortar to ensure stability. Details can be found under our sections dedicated to different bricks/stones.


Joint offset (not flush with the bricks)

The 'offset' of joints can be problematic. Joints can be flush with the brick surface, protrude, or be indented. This offset may prevent a uniform pressing of the rubber seals. Therefore, the joints should be made as flush with the brick as possible before installation-- either by sanding a protruding joint or by building a larger contact surface (using composite mortar). An offsest can also be remedied by inlaying small pieces of weatherproof rubber strips. Or, for a small extra charge, we can provide you with additional seals that you can cut to size!