Definition
Frailty or shortcoming of an item resulting from a defect in its concept, and which can be avoided only through an alteration or redesign of the item. 

Defects in design and engineering can be prohibitively costly to resolve.
Design defects in construction are defects that make a structure inherently unsuitable for its intended purpose, even when implementation of the design is executed correctly by builders and craftsmen. A serious design defect can be difficult and prohibitively expensive to resolve because it may require substantial modification and rebuilding of a structure.

Design Defects in Construction 

Failure to meet functional requirements
An example of a serious design defect in a home or office building is an architecturally unique roof design that leaks. While a design may be aesthetically appealing, if it leaks it is useless. The primary purpose of a roof on homes and office buildings is to protect the structure and its contents from weather, and especially rain. If it leaks, it fails to be suitable for its intended purpose and represents a serious design flaw. 

Failure to disclose design risks
Similarly, a cantilevered deck that is inadequately supported so that it places unusual stresses on other portions of a structure causing cracks in walls that need constant repair is a design defect. Good design practices must incorporate both aesthetic and functional considerations, as well as consider factors such as the structure soundness of a design and long term maintenance requirements. 

Design failures cause design defects
When architects, designers, or engineers fail to satisfy the functional requirements of a design, or when they fail to recognize and disclose potential risks associated with a design, the result can be a serious design defect for which they should be held accountable. Property owners should not have to bear the costs of resolving defects caused by careless design and engineering mistakes made by professionals who should know to avoid them. 

Typical Design Defects: 

• Building code compliance issues

• Insufficient and/or incomplete drawings

• Improper material specifications

• Roofing design defects

• Design and performance specifications

• Window/curtain wall design issues

• Building envelope design defects

• Approval of defective construction

• Performance and Payment Bond issues

• HVAC design problems

• Structural failures

• Subsurface soil matters