Improving quality assurance practices in the independent quality firm model for U.S. design-build projects

Purpose Major transportation infrastructure projects in the U.S. using design-build delivery may adopt independent quality firms in which construction engineering and inspection (CEI) firms are retained by design-builders to perform quality assurance (QA) tasks that have traditionally been performed or overseen by public owners. This contractual shift can create ambiguity when technical QA, documentation/payment support and contract-compliance responsibilities are bundled within independent quality firm scopes. This study examines how experienced transportation professionals interpret independent quality firm (IQF) roles, stringency and independence, focusing on areas in which responsibility boundaries are understood differently across stakeholder groups. Design/methodology/approach An exploratory sequential mixed-methods approach was used. Survey responses from five professional groups, including public owners, owner's representatives, general contractors, design consultants and CEI specialists, were analyzed descriptively, with Kruskal–Wallis and Dunn's tests used as exploratory indicators of divergent perception patterns. Additionally, 15 semi-structured interviews were thematically analyzed to contextualize the survey patterns and explain how practitioners interpret role boundaries, contractual authority and perceived independence. Findings IQF role ambiguity is most evident when responsibilities extend beyond technical QA into engineering judgment, payment documentation and contract-compliance tasks. Public-owner respondents reported greater perceived CEI leniency than most other professional groups, except general contractors, while several industry respondents viewed CEI stringency as comparable to or greater than under traditional QA. Interviewees discussed these perception patterns in relation to contractual scope, reporting lines, escalation authority and perceived independence. Originality/value This study refines the application of principal-agent theory to third-party quality oversight by conceptualizing the IQF as a design-builder-retained entity performing responsibilities tied to public-owner requirements. It distinguishes contractual independence from perceived independence and uses role clarity as an analytical lens for examining stakeholder interpretations of responsibility and authority boundaries across technical QA, documentation/payment support and contract-compliance tasks.