http://www.myfoundationrepairs.com/blog/post/2015/01/14/Structur

Know the Difference Between Structural and Non-Structural Cracks

Non-structural Cracks: Non-structural cracks are caused by changes in the moisture content and thermal movement. They can occur anywhere in the foundation wall where there are openings in the wall. Non-structural cracks can also be caused by the following conditions:

• Creep
• Vegetation/Trees
• Shifting or moving foundations
• Settlement
• Hydrostatic pressure

Some characteristics of non-structural cracks include:

• 1 to 2mm wide hairline cracks
• Cracks at the corners of doors and windows
• Vertical to diagonal cracks
• Cracks on plaster
• Narrow, less than 1/8"

Structural Cracks: Structural cracks are due to poor construction sites, swollen soil, poor soil bearing or overloading. These cracks are usually accompanied by other signs of foundation issues such as sticking doors and windows, slanted doors, sloping floors and cracks in porches.  The common characteristics structural cracks include:

• Continuous horizontal cracks along walls
• Vertical cracks that are wider at the top or bottom
• Stair-step cracks
• Foundation wall cracks
• Cracks in beams, foundation slabs
• Angled cracks that form in the corners of walls with a horizontal crack in the center
• Cracks wider than 1/8"
• Cracks extending to the upper levels of the home