Until I recently studied for the CDT exam*, I had considered QA (Quality Assurance) and QC (Quality Control) as synonymous – the same thing with different names. They are different, but they are closely related. Considering construction, QA establishes the standards to be met, and QC establishes the testing and inspection that will be done to verify compliance with the standards (QA). So QA informs QC by establishing the basis for QC measurement. And QC can provide feedback to strengthening QA. Specifiers are accustomed to including QA and QC requirements in project specifications, but designers may not appreciate the relationship between QA and QC as they relate to design firm activities.
Considering design and construction documents, QA can establish the standards to be met by the design and construction documents. These standards might include Owner design criteria and building standards, funding authority requirements, the design firm’s office standards, governing codes and regulations, sustainability standards, and other criteria. QA is up-front work and should be established early enough to guide the design work and development of construction documents. QC, on the other hand, consists primarily of review of the design and construction documents to verify compliance with the standards established at the outset (QA). QA informs QC about what to look for, and QC can inform QA about what should be modified or strengthened in terms of standards and enforcement of standards (e.g., training, mentoring, supervision, or scheduling). Effective supervision includes both QA and QC; it includes QA by communicating expectations (standards); and it includes QC through ongoing review of work to measure compliance with communicated expectations and standards. If QC indicates unacceptable results, it raises questions about the effectiveness of supervisory QA (“Oh, did I not tell you we wanted that?) or the readiness of the employee to perform the work (“Oh, I think you may need more training in that area.”).
Without effective QA, designers and drafters are likely to pursue their own personal ideas, and the resulting designs and construction documents may be inconsistent, uncoordinated, and out of compliance with standards that should have been communicated at the outset (QA).
The effectiveness of internal QC (testing by the installer or drawing review by design firm staff) can be limited by internal relationships. The installer may overlook a flaw in order to avoid the cost of correction. Design firm staff may overlook a design flaw in order to avoid confrontation or conflict with an office peer. QC is critical in nature, and some individuals are just plain uncomfortable in that role. QC can also be tedious work; that is another reason that it enjoys less attention than needed in some design firms.
QC by an independent party can be more objective, focusing on the work product instead of the individuals who performed the work. The objective, independent QC feedback can also inform and benefit design firm QA.