I have a crack in my concrete block garage wall .It starts where Brickie when building the wall 20 years ago fitted a vent in the line of second block from the top.The block above the vent was left without real support at one end and has dropped a bit and from that end of the vent aperture there is a zigzag crack down the wall to the floor.When I first noticed the crack appear I cut a brick to size and placed it in the aperture to support the dropped block and cemented up the crack.This seemed ok for some time but now I notice that the crack has opened again.
I hope I have been clear enough with my problem explanation and are there any suggestions on how to put things right.By the way the concrete floor is ok.