Stair Step Cracks
Sometimes the cracks in a brick wall take on a stair step shape, staggering down the wall in straight horizontal lines followed by a vertical line and then another horizontal line. This type of cracking indicates that some kind of settling is happening under your house. It could also mean your foundation is in a state of upheaval, which can be natural part of a home's growing pains, especially when it is first built, but if the cracks are wide, measuring more than 1/2 inch, the problems could be serious and costly.
Vertical cracks in your brick walls are a serious sign of trouble, especially if you notice the separation at the cracks are wider at either the top of the bottom. A crack with a wider gap at the top that extends straight down a wall vertically likely means the foundation is dropping at that end of the house, or the middle of the foundation is rising for some reason. The same crack with a wider gap at the bottom indicates the opposite, meaning the other side of the foundation is dropping or the center of the foundation is dropping.
Wide Gaps Above Doors
You may have had inept or careless builders if you start seeing wide angular cracks form above the doorways in your home. These danger signs point to severe settlement issues with the house that result from improperly building in joints or other structural essentials, which is true of any wall, whether the interior or exterior walls are brick, plaster or otherwise.
What to Do
If your home has cracks in brick walls that you suspect are being caused by foundation or settling issues, you shouldn't ignore them. Repairing these cracks will not solve the problem as they are likely to reappear as the foundation moves again. If your house is new, you should contact the builder and let him know you have concerns about the structure; otherwise you should contact a structural engineer and ask for an inspection. The remedy may be anything from adjusting the soil around your foundation to underpinning using piers.