1. Cracks in concrete slabs - classified as structural and non-structural. Hairline cracks in concrete slabs may be regarded as a natural facet of concrete and not as a defect. If the crack size is stable and there isn't excessive separation (vertically or horizontally), then the crack is probably non-structural. On the other hand, if the sizes of the cracks are changing, and/or indications of movement of the slab exists, a qualified structural engineer should be consulted.
2. Cracks in exterior walls - in wood frame, stucco, and masonry homes, hairline cracking is quite common. However, cracks that are 1/8 inch wide or larger may be an indication of structural concern and should be reviewed by a qualified structural engineer.
3. Cracks in interior walls - are often found at corners of openings and walls. A qualified structural engineer should review large cracks.
4. Sagging roofs or floors - can be a sign that structural members are over-stressed.
Excessive sagging of roof members could cause pooling of water on the roof, which may cause structural problems. A qualified structural engineer must review such items.
5. Improper drainage - is one of the most common problems that exists in homes, and is caused by poor grading of the ground adjacent to the home. All driveways, sidewalks, planters, and yards should slope away from the home's foundation for at least 5 to 10 feet. If moisture is kept away from the foundation, there will be less movement within the structure and fewer cracks. This becomes extremely important for those foundations that are located on expansive and/or collapsible soils.
6. Termite damage - if termites have damaged the home (as reviewed by your termite inspector) all repairs must be made. Unrepaired damage could lead to further structural problems in the future.
If you have any questions or concerns about the structural soundness of the property that you own or are about to own, consult a qualified structural engineer. The concerns you have may be minor, but there could be a major structural problem. Consulting with a qualified structural engineer will protect your investment and give you peace of mind.