High-volume home building (those homes built in large subdivisions by large homebuilders) in the United States has undergone a gradual increase in construction cycle time from start to closing over the last two decades. Part of the increase may be attributable to a concomitant increase in the size and complexity of the typical production home. Cycle times on the order of 2 months were common 20 to 30 years ago in the industry, whereas 6 to 8 months is more common at present; this dramatic increase cannot be explained by differences in the size and specification of the homes being built alone. Most large production homebuilders in the United States have discontinued the practice of self-performing work on their projects, and instead rely upon a network of highly specialized subcontractors organized by trade or activity. This change was motivated by the search for efficiency and cost reduction at the individual task level. In the present production system, 30 to 40 individual subcontractors must be coordinated to complete 100 to 150 separate activities at the home site. Typical value-stream maps of portions of the residential process are presented, illustrating the large number of interfaces or handoffs between organizations which result in the production system. Substantial quantities of wasted time are documented in the production process based on field observation. Much of the wasted time can be attributed to the large number of interfaces and the time-gating strategy of turning over each home to each trade in one day increments. The implications are demonstrated conceptually and quantitative results are derived from process simulation. The paper provides suggested modifications to the production system to reduce cycle time, even assuming existing production methods (at the activity level) are maintained.
Residential construction, production systems, process mapping.