Question 6 of 6: Productivity — influencing factors, measurement and improvement

Question 6: Productivity — influencing factors, measurement and improvement (20 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

Labour productivity is the ratio of work put in place to the labour effort consumed — conventionally expressed as work-hours per unit of output, so that a falling number means improving performance. It is the most volatile item in a construction estimate and the one over which the contractor has the most control: material prices and equipment rates are set by the market, but the number of work-hours it takes to place a cubic metre of concrete is set by how the project is managed. It is also the item most often blamed after the fact and least often measured during the work, which is why the question asks for measurement as well as causes.

Factors affecting productivity. The influences group naturally under five headings. Management and planning factors dominate the empirical studies: the availability of materials, tools and information at the workface; the quality and timeliness of drawings; the sequencing of trades so that crews are not stacked into the same space; crew size and composition relative to the work available; and the presence of competent front-line supervision. A crew waiting for a hoist, a permit or an answer to a request for information is unproductive for reasons that have nothing to do with its skill. Labour factors include skill level and experience, training, motivation and morale, turnover and absenteeism, the learning curve on repetitive work, and labour-relations conditions. Project and design factors include the complexity and buildability of the design, the degree of repetition, late design changes and rework, the tightness of the site and access to it, and the extent of prefabrication. Environmental factors include temperature, precipitation and wind, dust, noise and daylight — particularly significant in Canada, where winter work brings heated hoardings, cold-weather concreting and the productivity penalty of heavy clothing — along with site congestion and the interference of adjacent operations or, on highway work, live traffic. External factors include regulatory and inspection delays, permits, utility relocations, third-party approvals and community constraints such as restricted working hours. Two composite effects deserve separate mention because they are large and routinely underestimated: overtime, where sustained scheduled overtime beyond a few weeks produces well-documented efficiency losses through fatigue, absenteeism and pace-slackening; and trade stacking and acceleration, where compressing a schedule by adding crews into a fixed space reduces the output of every crew present.

How productivity is measured. The basic unit rate — work-hours divided by quantity installed — is computed for each work package from timesheets and quantity surveys and compared with the estimated rate; the ratio of actual to estimated is the productivity factor, and a value above 1.0 signals trouble. Because unit rates are only meaningful after a quantity has been installed, they are supplemented by leading measures. Earned value analysis converts installed quantity into earned hours or dollars and computes a cost performance index and schedule performance index, giving a trend early enough to act on. Work sampling and the five-minute rating use randomised observations of crews to classify time as direct work, essential support or delay, and typically reveal that direct work occupies only 30 to 45 per cent of the day — the diagnostic value being in the composition of the remainder. Craftsman questionnaires and foreman-delay surveys ask the workers themselves what stopped them, which is usually the cheapest and most accurate source of the causes. Time-lapse photography and video, and increasingly automated sensing, document cyclical operations for method study. At the project level, benchmarking against organisational or industry databases such as those maintained by the Construction Industry Institute puts the numbers in context. In all cases the measurement must be defined consistently — the same work-hour boundaries, the same quantity definitions — or period-to-period comparison is meaningless.

Ways to improve productivity. Improvement follows the measurement, and the highest-return actions are almost always about removing waiting rather than working faster. Pre-construction planning and constructability review eliminate rework before it is designed in. Short-interval planning — the weekly work plan and the make-ready look-ahead of the Last Planner System — ensures that no task is released to a crew until its materials, information, equipment, access and predecessor work are confirmed, which directly attacks the largest category of lost time. Site layout and materials management shorten travel and handling: laydown near the workface, kitting, and just-in-time delivery. Prefabrication and modularisation move work from a congested, weather-exposed site into a controlled shop. Method study and mechanisation improve the cycle itself. Balanced crew sizing and levelled resource histograms avoid both idleness and overcrowding. Training, apprenticeship and stable crews build the learning curve rather than restarting it. Realistic scheduling avoids the acceleration and trade-stacking losses that acceleration is supposed to fix. Incentive and gain-sharing schemes can help where output is measurable and quality is not compromised. Finally, feedback closes the loop: reporting measured productivity back to foremen weekly, and recording the resulting unit rates in a historical database, improves both this project's performance and the accuracy of the next estimate.