A productivity measurement framework for construction projects

Abstract

Around the world, productivity (i.e. output generated per unit input) in the construction industry has been shown to lag behind many other industrial sectors. In the UK, it has essentially flat-lined for the last 25 or more years, while some sectors, such as manufacturing, have improved by over 2.5-fold during the same period. With construction contributing over 6% of the gross domestic product and 25% of greenhouse gas emissions in the UK, the economic and societal gains from even modest improvements in construction productivity are enormous. For example, if the productivity of the UK’s construction sector improved by just 5% over the next year, the potential savings could be over £7 billion. Thus, improving productivity in the construction sector is one of the highest political priorities for the government in the UK, as well as many other countries around the world. So, what can be done? Peter F. Drucker is often attributed with the quote, “What gets measured gets managed.” Thus, the first step in improving productivity in the construction sector is to measure it. The statistics agencies of many countries already measure productivity at the industry level (i.e. considering a country’s construction industry as a whole). However, to identify the reasons for low productivity, it should be measured at more detailed levels, such as individual construction organisations or projects, which form a country’s construction industry. A systematic review of over 100 papers in the area identified a large body of academic work on measuring construction productivity but found few examples of any method being widely adopted in practice in construction organisations or projects in the UK or elsewhere in the world. In most cases, this was found to be partly due to the lack of available site data for the metrics and also due to the difficulty and impracticality of obtaining and measuring the parameters proposed in these measurement schemes. In parallel, a detailed survey of industry personnel, along with a series of interviews with key stakeholders in the value chain, was conducted to learn what data and measures of productivity were currently being collected and utilised in the industry. This research project has developed a generic, consistent and practical framework for measuring the performance and hence productivity of construction projects. It seeks to provide a tool that could be applied across all construction sectors, although in this thesis it has been derived predominantly for use on commercial/residential multistorey framed buildings, allowing a fully worked-through methodology to be produced down to a very granular level of detail. This framework was deployed for use on 22 individual buildings in the UK to demonstrate its use and gauge the response of the end users to the value created by this approach. In addition to quantitative productivity data, various qualitative data were also collected to identify reasons for low productivity. The application of this productivity measurement framework to multistorey framed buildings led to many findings. Notably, it was discovered that offsite construction/prefabrication, often cited as a means for improving construction productivity, only led to a decrease in the onsite workforce required for constructing a building but did not improve speed or reduce costs. It should be noted that the lack of effect on speed was mainly due to supply chain issues such as design and factory delays of offsite components, and not necessarily due to poor onsite performance. One of the unique features of this framework was its consideration of productivity losses at the interfaces between individual construction activities, which are typically not addressed in productivity literature. It was discovered that one of the largest causes of poor onsite productivity was work crews spending too much time without work available between activities due to poor planning. This issue was even more significant than the slow speed of performing individual activities. Several underlying industry issues were uncovered in this research that help explain the poor performance of the construction industry. First, planners from multiple construction organisations were found to intentionally produce unfeasible construction schedules to secure contracts, leading to delays and cost overruns when the planned schedule, which was used for project costing, could not be met. Secondly, the main (i.e. Tier 1) contractors were found to contractually transfer the responsibility of managing labourers to subcontractor organisations, which lacked the resources to effectively track them. This resulted in a significant waste of worker-hours on sites, ultimately leading to poor productivity. As a result, the framework introduced here, if widely implemented, has the potential to provide insights into and an understanding of where productivity can be improved, thereby leading to an overall enhancement in the level of performance within the construction industry.