13 Quality Control During Construction
13.1 Quality Concerns in Construction
Defects or failures in constructed facilities can result in very large costs. Even with minor defects, rework (re-construction) may be required, and facility operations may be impaired. Increased costs and delays are the result. Hwang et al studied 359 construction projects to analyze the sources of rework. Its measured impact typically adds up to 5% of the total project cost, and experienced project managers estimate the real percentage is often much higher. Contrast that with typical profit margins of only a few percent of total project cost. Good project managers try to ensure that the job is done right the first time. Quality control is essential in that regard.
As with cost control, the most important decisions regarding the quality of a completed facility are made during the design and planning stages rather than during construction. It is during these preliminary stages that component configurations, material specifications and functional performance are decided. Quality control during construction consists largely of insuring conformance to these original design and planning decisions.
While conformance to existing design decisions is the primary focus of quality control, there are exceptions to this rule. First, unforeseen circumstances, incorrect design decisions or changes desired by an owner in the facility function may require re-evaluation of design decisions during the course of construction. While these changes may be motivated by the concern for quality, they represent occasions for re-design with all the attendant objectives and constraints.
As a second case, and it is not the focus of this chapter, some designs rely upon informed and appropriate decision making during the construction process itself. In many ways, the submittals process in building construction reflects this fact. The owner’s architect and engineer will specify equipment (such as cooling equipment, window systems, etc.) and materials (such as floor finishes, hardware and furnishings) in general terms of performance and quality. Just before and during construction, the contractor will submit specific product options with their performance specifications and prices to the owner or their AE firm for approval. This leads to the classic conpcept of the quality-cost-schedule trade-off triangle shared in many construction project management text books, however “quality” in this context is defined as the architectural massing and design, richness and finish of materials, craftsmanship, landscaping and other aspects of the building. In this chapter, we are focused on conformance to design intent.
With the attention to conformance as the measure of quality during the construction process, the specification of quality requirements in the design and contract documentation becomes extremely important. Quality requirements should be clear and verifiable, so that all parties in the project can unders