Here is a comprehensive list of things to be on the lookout for when dealing with your foundation:

• Cracks on the inside walls
  Corners of windows will often crack horizontally and doors shift out of their frames and do not shut properly.
• Cracks on the fireplace bricks and other masonry
  Bricks are more stable than drywall, so when they start to crack, you know you have a serious problem.
• Nail heads poking out backward
  This is an indication that your gypsum board is bending, leaning, or sinking depending on the movements of the house.
• Windows and doors no longer fit in their frames
  If your windows and doors are popping out or no longer fit in their frames, this is a very bad sign. Try opening and closing all windows and doors to test for this.
• Windows on the outside of the house are experiencing diagonal cracking
  The caulk joints could be being pulled apart on these windows, which is why they will crack differently than inside windows.
• The visible concrete at the base of the home begins to fracture
  This could be nothing more than settling, especially if the cracking is small. Be sure to check with an inspector to be sure.
• Rainwater not draining properly, resulting in standing water around the home
  This is probably the result of improper drainage, and should also be taken care of immediately.
• Trees that are very close to the home
  Roots from large, old trees have a tendency to go where they please, which can be problematic.

These issues should not be dealt with lightly. Cracks on the interior walls are not only ugly but decrease the value of the home, while cracks in the brick allow the wind and weather to penetrate your outside walls. Improper fitting doors and windows allow the inside air comfort out resulting in unpleasant drafts and higher heating and cooling bills. Leaks in the roof cause water damage to the wooden support beams, insulation, interior walls, ceiling, and electrical wiring.

All of these things are early warning signs of impending foundation distress. If your home is built on expansive soil, chances are you will experience some form of foundation distress, for sixty percent of all homes built on expansive soil experience it at some point. Foundation settling or moving in and of itself is not a bad thing. The part that causes damage is when only a small section of the foundation raises or settles, which causes fractures and other damage.

The movement of the foundation is largely caused by differences in soil moisture. Additional soil moisture results in shrinkage and swelling.

Settlement cracks are nearly always vertical, and should not be confused with cracks that occur when a wall is subjected to lateral movement from soil pressure. The soil underneath your foundation expands when it's wet and contracts when it's dry, which can potentially shift sections of your foundation. Foundation problems can occur if sections of the soil are not compacted properly, causing parts of the house to settle.