In construction cost estimating, productivity factors are critical in the unit rate build-up. They ensure that estimates are not just the theoretical time required to complete a task but also the actual conditions and challenges of the site.
A unit rate might start with a baseline productivity assumption (for example, square metres laid per hour). However, this starting point must be adjusted to account for real-world conditions. Failing to do so can result in inaccurate estimates: either underestimating labour time and cost or overcompensating, which can inflate the tender price beyond competitive levels.
As we’ve mentioned in these Quick Takes, the core objective of the estimating process is to determine, as closely as possible, the actual cost to build. This cannot be emphasised enough: this is the cost you or your company can realistically deliver the described work for.
Only after this cost is established should considerations such as competitiveness, profit margins, or pricing strategy be added. This final layer is addressed during management’s tender adjudication, where the cost you’ve developed is reviewed, and any necessary adjustments for margin or market positioning are applied.
What is productivity in construction?
In construction, productivity refers to the amount of work completed per unit of input. It is usually measured as output per labour hour.
For example, how many square metres of flooring can a crew install in an hour?
Unfortunately, productivity on-site is rarely straightforward. While standard or “ideal” rates are derived from manuals or supplier data, they seldom capture the complexities of each project.
Estimators must consider that productivity is influenced by various factors. Team experience, past history, site layout, weather conditions, material availability, and access constraints all affect productivity.
Recognising these influences is essential when building up unit rates. It ensures the estimate reflects not just what could be achieved in perfect conditions but what is likely achievable on a specific site under specific circumstances.
Key Components of Productivity Factors
- Historical Performance Data
Estimators often rely on data from past projects to establish realistic productivity benchmarks. For example, records may show that under typical conditions, a team installs 12 m² of brickwork per hour. This historical average forms the baseline when pricing similar future work. - Site-Specific Adjustments
No two sites are identical – Restricted site access, tight working spaces, weather exposure, or challenging ground conditions can significantly reduce output. Estimators apply adjustment factors to the baseline productivity to account for these realities, ensuring that unit rates reflect the unique challenges of each project.
Allowances for Downtime and Inefficiencies
Even with meticulous planning, some downtime is unavoidable. This can be due to material deliveries, equipment setup, safety briefings, or unexpected delays. By accounting for these inefficiencies, the estimated labour hours will more accurately reflect the actual work on-site.
Example: Applying Productivity Factors
Let’s consider a crew laying concrete blocks: Under open, unobstructed conditions, they might achieve a productivity rate of 15m²/hour. However, if the project site has narrow access ways, tight scaffolding setups, or requires materials to be manually lifted over obstacles, productivity might drop to 10m²/hour.
When preparing the unit rate, the estimator adjusts the labour input to reflect this reduced productivity. Instead of pricing the work based on the ideal rate, they calculate the labour hours and cost using the adjusted, site-specific rate. This approach ensures that the final unit rate realistically covers the time and cost required to complete the task under the actual conditions expected on site.
Why It Matters
Accurately adjusting for productivity is essential to producing fair, competitive, and sustainable unit rates.
If productivity is overestimated: Labour costs will be too low, eroding profit margins and potentially leading to cost overruns.
If productivity is underestimated: The unit rates may become uncompetitive, putting the tender at risk.
If an Estimator applies productivity factors using historical data, site-specific insights, and realistic allowances for downtime. It ensures the pricing reflects the true demands of the project.
This not only supports sound financial planning. It also strengthens the contractor’s reputation for delivering on time and within budget.
Additional Reading:
Study on: Factors to improve productivity in NZ construction
