Brickwall cracking and identifying patterns

I was looking thru a post from a structural engineer on LinkedIn and have uploaded the photographs form his LinkedIn post above. I noticed that they were underpinning an existing building due in some part to the attached photographs, and it got me thinking about crack patterns and what type of crack patterns best identify what is happening during an investigation.

I know that there aren’t any hard and fast rules on cracking, generally, it will follow the stress location a the weakest point. However thought it would be good to discuss what type of crack patterns people identify with, below is a short summary to get the conversation started.

  1. Vertical Cracks
  • both straight and brick toothed - brick growth if ht crack is a common thickness

  • straight but tapering from top to bottom - soil moment

  1. Horizontal Cracks
  • due to the brick wall out of plan moment, not enough support for the wall in EQ or wind
  1. Diagonal Cracks

-soil heave/shrinkage type movements.

  • at windows thermal, if they tend to go to the ground.

There’s only one or two cracks which appear to be structural, namely the vertical crack near a corner under a window. It looks like a frost crack, but it is a bit hard to say.

Cracking at the ends of the long lintel could be the result of excessive deflection and rotation of the lintel.

Otherwise, there seems to be some mottled discoloration on the surface of the brick or nominal cracking which is difficult to identify clearly from the photographs provided.

As a non-CE I tend to run with ‘gravity is at work here’. Could the one case be about the window, as in one wall moving relative to the one at right angle to it? Could it have been possible to concentrate weight away from the far corner?

The one at the corner looks wider at the top than the bottom. Possibly some rotational settlement here…

What would be the nature of the rotation? The narrow stack (right of the crack) is definitely lower than the rest of the facing wall. Can we guess the holes are dug for reinforcing the foundation?