House completion time in Australia: workflow planning approach

The Australian house building industry has seen an increase in the average house completion time in the past decade. This increase in some Australian states was quite dramatic. For instance, Western Australia faced a seventy percent increase in the average house completion time during this period. Since houses make up more than seventy-five percent of dwellings in Australia, this increase affected a large proportion of housing supply in the country.

This research addresses this issue at industry and company level by investigating house completion time using a workflow-based planning approach. For this purpose, a national and five State case studies (Victoria, New South Wales, Queensland, Western Australia and South Australia) are used at industry level. At company level, production house building is adopted for the study.

The research starts with possible explanations for changes in house completion time suggested by activity-based and workflow-based planning approaches. Investigation of the relationship between average house completion time, number of house completions and number of houses under construction is undertaken by comparison between predicted number of houses under construction using Little’s law and actual data. Research at company level includes modelling of an actual house building process, simulation of different operational strategies and exploration of their effects on house completion time. The strategies investigated in the research are the control of workflow, control on construction commencement and having different house options in the process.

The result of research at industry level shows that there is a strong correlation between average house completion time and number of houses under construction. Little’s law predicts the number of houses under construction by a small error and it holds true for the national and State house building industries. The existence of a two-phase relationship between house completion time and number of houses under construction is demonstrated and house building industry capacity is estimated for the whole country and different States. This is the maximum number of houses that the industry can work on without increasing the completion time.

At company level, the simulation of different levels of workflow shows that constant workflow returns constant completion time. Reducing the construction commencement intervals in order to achieve higher resource utilization may increase house completion time dramatically. Further, when the new house option is smaller than the current options, its completion time fluctuates between its minimum completion time and the completion time of the largest house option. The modelling also shows that, in the case of the launch of a house option larger than the current options, queues in the production operation are inevitable and the completion time of all house options grows infinitely.

To summarise, the research investigates house completion time in Australia and highlights the effect of workflow on this parameter at industry and company level. It demonstrates the applicability of a workflow-based planning approach in the house building industry and recommends it for use by housing policy makers, house builders and housing researchers for analysis of industry’s dynamics and understanding of house building process.