A material defect is defined in the InterNACHI® Home Inspection Standards of Practice (www.nachi.org/sop).
A “material defect” is a specific issue with a system or component of a house that may have a significant, adverse impact on the value of the property, or that poses an unreasonable risk to people.
An example of a material defect is a wooden deck that is in such poor condition that it poses an unreasonable risk to someone using it. The inspection image is of an attached deck and stairway that is about to collapse.