Quantitative performance assessment of single-step versus two-step design-build procurement

Design-build (DB) is an alternative project delivery system that is distinguished by a DB team acting as the single point of responsibility for a project in which the design and construction phases overlap. There are two main methods used to procure DB services: single-step and two-step procurement. Single-step DB involves a request for proposal (RFP) phase, whereas two-step DB involves both request for qualifications (RFQ) and RFP phases. There is an industry perception that more resources are spent to procure single-step DB projects as compared with two-step DB projects. Therefore, this paper focuses on quantifying the resource expenditures and efficiency impacts of single-step and two-step DB through investigating several procurement and project performance metrics. The paper presents results stemming from 32 completed projects. The results of the analysis show that the total cost to industry to develop single-step proposals is approximately 5% of the total project cost, whereas the cost to develop two-step proposals is approximately 1% of the total project cost. Additionally, the relative procurement duration was 18% of the total project time for single-step DB and 22% of the total project time for two-step DB. Moreover, the percentage of design completed at the RFP and award stages are presented. For single-step DB, 23% of the design was completed at the RFP stage, and 43% at the award stage. For two-step DB, 12% of the design was completed at the RFP stage, and 32% at the award stage. Most importantly, the findings contribute to the DB body of knowledge by quantifying a significant five-fold procurement cost difference between the two DB procurement methods, helping the industry implement procurement policy changes.