Weak Routes

Openings in walls for windows and doors reduce the strength of brickwork. The direction of the crack may be distorted by relative position of openings within a wall or elevation of a building. The tension force will cause failure along the weakest route. Depending on the relative position of the openings, the angle of the crack might be made more horizontal or more vertical, than would otherwise be the case.

 

Weak Routes

 

Buildings usually have openings in the walls, for windows and doors. Where there is an opening in the wall, the strength of the brickwork is reduced. The tension force will overcome the ability of the brickwork to resist it, along the line of the weakest route. Depending on the position of the openings, this will alter the angle of the crack pattern.

Although the angle of the cracks shown in the picture is different, they are, after allowance for weak routes, the same crack.