Construction quality assurance (QA) is the systematic process of verifying that construction work meets specified standards at the phase where verification is possible and correction is still practical. It operates at two levels: specification QA (using the correct materials and methods for the project’s specific conditions — the cheapest form of QA because specification errors are free to correct before work begins) and execution QA (verifying that specified materials and methods are actually installed correctly before the work is concealed — much cheaper than post-occupancy correction). An effective QA program has three tiers: specification-level QA at the estimate stage; phase-level QA at each trade handoff while the wall is open; and punch list QA at project completion. The economic rationale is the cost-of-quality curve: defects caught at their phase of origin cost the least; defects that survive to the punch list cost 10–20× more; defects discovered after occupancy cost even more and damage the client relationship permanently.