The mortar and joints around a coping stone are so important in order to preserve the render on a wall.
The top surface of a wall is the most vulnerable point for water to enter a building. Over time, the joints and mortar around a coping stone wear and loosen due to years of weathering. When this happens, water can easily get through and into the walls which is where the problems begin.
Once water is allowed through to the wall, it pushes down to the furthest possible point – the foundation – and sits here, where it doesn’t have anywhere else to go. Render on the walls makes the problem worse as it traps the water in this space. Damp is caused by the water that is trapped because once the water has nowhere else to go, it begins to rise back up. The damp then damages the brickwork and in time this damages the render. It begins to fall off the wall.
This means that not only does the render have to be repaired but also the wall. By maintaining the mortar around the coping stone, you prevent any water from getting inside the wall and therefore any of this damage to the render from happening.