I frequently get shown examples of fall arrest systems or abseil anchors attached to the top or inner face of parapet walls.
The installer may think that if they pull test the anchor points against the masonry – this proves the fix is adequate. However, this only tests the adherence of the anchor not the strength of the masonry and does not accurately represent the applied load.
In the case of a 6 – 15kN load being applied to a coping stone it is highly likely to dislodge as it is head in place generally by its’ dead weight alone. Leading to the potential for it to fail land on a user if a fall were to occur.
Likewise, the flexural strength of masonry is related to the applied dead load, so a parapet wall is week in the direction perpendicular to the wall.
In short most masonry parapet walls require reinforcing to carry the loads associated with height safety equipment and generally the roof structure provides a better fix position.