Productivity mapping and literature review
The University of Dundee, in association with Whole Life Consultants Ltd, was commissioned by Built Environment – Smarter Transformation (BE-ST, formerly Construction Scotland Innovation Centre) on behalf of the AIMCH partners to undertake a wide-ranging literature research analysis and compile a report focused on construction productivity measurement studies and protocols.
The AIMCH project aims to help tackle the UK housing crisis by using industrialised offsite solutions to deliver high quality homes faster, more reliably and at the same cost as masonry-built homes.
The aim of the literature review was to help the AIMCH partners understand the current landscape of productivity metrics and future trends, and to enable them to gain a good understanding of key tools and techniques in all areas of monitoring. The outputs will be used to inform and influence the way in which the partners choose to measure their on-site activities.
summary
The report begins by providing guidance on the choice of metrics that were used, leading and lagging indicators, the appropriate level of detail and the level of alignment with suggestions provided by industry and government bodies such as the Construction Leadership Council.
This is followed by a section dedicated to each of the principal metrics. Each section is structured as follows:
- General remarks
- List of each performance metric considered
- Description of each of the recommended metrics and method of measurement, together with an assessment of the merits and disadvantages. This area also includes details on the level of uptake and/or examples where it has been used. (Similar information for metrics which were not recommended for use are included in an Appendix.)
- Summary of the relative merits, in the opinion of the research team, of each of the metrics in the previous section
- Recommendation as to which metric should be considered for use and in which circumstances with an accompanying rationale
In addition, sections on emerging technologies and the findings of earlier studies are included.
To ensure clarity and avoid ambiguity, an agreed Glossary of Terms has been provided, together with a list of criteria against which each performance metric should be assessed.
Principal Metrics
The principal metrics considered were:
- 1
- Safety
- 2
- Productivity including labour productivity
- 3
- Quality including rework, defects and reliability
- 4
- Cost including cost/m2, cost per unit, cost effectiveness
- 5
- Time including duration (normalised to take account of differences in design) and percentage of milestones achieved (including planned completion dates)
- 6
- Predictability of time and cost
- 7
- Efficiency
- 8
- Material waste
In all, 66 metrics were reviewed.
- 1Safety;
- 2Productivity including labour productivity;
- 3Quality including rework, defects and reliability;
- 4Cost including cost/m2, cost per unit, cost effectiveness;
- 5Time including duration (normalised to take account of differences in design) and percentage of milestones achieved (including planned completion dates);
- 6Predictability of time and cost;
- 7Efficiency;
- 8Material waste.
In all, 66 metrics were reviewed.
Findings
-
Safety
Two leading metrics were recommended:
- Percentage of audited items in compliance;and
- percentage of tasks which are pre-planned.
The use of one lagging metric was also recommended:
- Frequency rates, and in particular, number of days of lost work per 100,000 hours worked.
It was further recommended that consideration should be given to supplementing this metric with the number of accident near misses recorded per 100,000 hours worked.
-
Productivity
For the measurement of productivity, the following recommendation were made.
- If detailed information about the process of construction, its context and constraints is required, and if the labour force cannot be used to keep the necessary records, then direct, continuous observation by a trained observer should be used; and
- If the purpose is simply to determine the reduction in labour inputs occasioned by off-site manufacture, then the use of radio-frequency identification (RFID) or Bluetooth Low Energy (BLE) technology should be piloted.
In any case, it would be advantageous, not only to the AIMCH project but to the whole industry if RFID were supplemented by direct observations and activity sampling so the relative merits of each approach could be determined in more depth.
-
Quality
For the measurement of quality, the use of the Home Builders Federation Star Rating, the NHBC Quality Rating, and the number of reportable items was recommended.
-
Cost
For cost, the recommended metrics were the average construction cost per plot and the average cost of rectification of defects per plot. To compare the costs of individual elements (eg walls, roofs), it would be necessary to collect construction costs related solely to those elements. To accomplish this, it may well be necessary to carry out direct observations.
-
Time
The recommended high-level metric was the average elapsed construction time per plot. If the time required to construct individual elements were the focus of attention, it would be necessary to record the start and completion times of each relevant activity. This may be achieved by the operatives themselves, by supervisors or by intermittent or continuous observations by an independent observer. -
Predictability
Time and cost predictability should both be measured in terms of the average percentage overrun. For complete houses, it should be measured at the plot level (ie average percentage overrun per plot). It can however be measured in the same way for any element or activity in the construction process eg walls, floors, roofs.
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Efficiency
It was suggested that metrics describing wastage in labour, plant, material and finance are developed on a case by case basis taking inspiration from lean thinking in sectors such as manufacturing where, for example, the efficiency of a plant is often described by the so called “down time”. When no other viable option is available, the adoption of percentage margin was suggested as an umbrella metric for efficiency whilst recognising that it is also a measure of ‘efficiency’ of the whole process including for instance sales and marketing.
-
Material waste
The most relevant metric identified was the net waste measured as the difference between the ‘value of materials not incorporated in the construction works’ and the ‘value of additional recovered materials incorporated in the construction works or in off-site applications’.
Conclusion
The choice of metric is critically dependent on the strategic objectives. Since different organisations have different objectives, it is unlikely that a single set of metrics will find ready acceptance. However, the report provides comprehensive evidence on which to base decisions about which metric should be used in which circumstance.
We recommend that each partner carefully reviews the recommendations we have made together with the underlying rationale, and checks that the metrics proposed satisfy both their strategic objectives and any internal constraints that may apply.
