When the construction site lies idle – and the factory can pick up pace

The next leap in construction efficiency is not happening at the construction site – but in the factory. Research documents that the construction industry is facing problems with large amounts of wasted time. Prefabrication may be a key tool for reducing wasted time and creating more efficient construction projects.

At Green Box, we develop and produce prefabricated bathrooms, and we see in practice that much construction project complexity can be reduced if work is relocated from the construction site to the factory. In a controlled production environment, planning, coordination and logistics can be done much more accurately – and precisely these areas are among the biggest time wasters at construction sites.

This is confirmed by research conducted by VTT Technical Research Centre of Finland, which has mapped the working day of workers at several construction sites in Finland. This research showed that only around one in five working hours is spent on direct installation work, with the rest being spent on preparations, handling of materials, coordination and interruptions.

The Finnish results are in line with Danish studies from the Department of Engineering at Aarhus University, where researchers have also documented a significant efficiency potential in construction projects. According to the study, only about a third of construction workers’ working time is spent on value-adding activities, while the rest is spent on support functions, waiting time and coordination. The researchers stress that this is not about making the workers work faster or harder – it is about creating better settings and workflows that make the work more cohesive and efficient.

Overall, both the Danish and Finnish analyses highlight the same pattern: that a large part of wasted time in construction projects occurs in connection with the many interruptions, handling of materials and interfaces between trades. This is precisely where prefabrication can be an effective tool: by moving parts of the work from site to factory, construction work can become faster, more predictable and, in many cases, also more sustainable.

Where wasted time occurs – and where solutions are found

Much of the inefficiency at construction sites is due to uncoordinated workflows and repeated interruptions. Construction workers have to wait for materials, move about at the site, adapt to cramped spaces or wait for workmen from other trades. The problem rarely concerns a lack of expertise – it is instead connected with the framework in which the work is performed.

Prefabrication moves a significant part of this complexity away from the construction site and into a controlled production environment, where work processes can be planned and repeated. A specific example is prefabricated bathrooms – some of the most technically complex rooms in construction projects – which are increasingly being produced ready-made in factories. This reduces the need for coordination, waiting time and troubleshooting on site.

When construction processes are moved from an open construction site to a controlled production environment, both the rhythm and precision of the work change. This applies especially to complex rooms like bathrooms, where many technical installations and trades need to interact. In the factory, the entire room can be completed in one streamlined process instead of through many separate workflows at the construction site.

The result is a more efficient process with fewer interruptions, less need for coordination and a more predictable flow from start to finish.

Factory systematics boost construction efficiency

When parts of the construction process are relocated from the more variable construction site conditions to a controlled production environment, the whole logic behind the work changes. Here, processes can be planned, repeated and optimised – in line with the lean principles of precision, standardisation and continuous improvements that have created high efficiency in manufacturing industry for many years.

Prefabrication makes it possible to transfer these principles to the construction industry. For example, when a bathroom module is delivered prefabricated, it simply needs to be connected to on-site installations. This frees up time and resources, makes planning more predictable and increases the quality of the finished building. At the same time, it shows how the construction industry can take inspiration from the manufacturing industry: with fixed processes, continuous learning and quality control that make it possible to deliver on both time and quality – even in complex construction projects.

Sustainability and stricter climate requirements

In addition to time and cost benefits, prefabrication can also contribute to more sustainable construction. Production in controlled surroundings typically reduces waste of materials, optimises logistics and minimises the need for transport – all factors that contribute to a lower carbon footprint.

With the stricter climate requirements in the Danish Building Regulations, which entered into force on 1 July 2025, emissions from the transport of building materials must now be documented and included in the life cycle assessment (LCA) of the building for a large part of the Danish construction industry. This entails more stringent requirements for documentation, planning and well-considered choices of materials and logistics.

When transport becomes a clear part of the green accounts, greater importance are attached to choice of suppliers and transport distances in the decisions made. Choosing suppliers with production close to the geographical location of the project can reduce transport-related emissions while also ensuring a more efficient and stable supply chain – an important step towards more climate-friendly construction.

More efficient and robust construction

For contractors, developers and consultants alike, prefabrication is not just about engineering, but also about strategy. Construction site operations are very costly, and every on-site day costs significant amounts in terms of manpower, logistics and equipment. When a construction project can be completed more quickly, the finances, planning and quality of the project become more robust.

By relocating more work from construction site to factory, the construction industry can take a decisive step towards higher productivity, lower carbon emissions and fewer bottlenecks.

Prefabrication does not change the craftsmanship – but the framework for it. Moving more of the work to the factory frees up on-site resources and makes the construction project more stable, predictable and sustainable. For us, it is not just about producing bathrooms but about contributing to more efficient and robust buildings – a necessary step for the whole construction industry.

Sources:

Erik Holm: “Spotify og konstante afbrydelser: Det flyder med spildtid på byggepladserne” (Spotify and continuous interruptions: There are massive amounts of wasted time at construction sites), Licitationen.dk, 2 October 2025

Christopher Görsch, VTT Technical Research Centre of Finland, 2024

ReVALUE, research project at Aarhus University (Department of Civil and Architectural Engineering) with Professor Søren Wandahl as project manager – productivity and wasted time studies in the construction industry, 2016-2019

Jesper Bruun: “Kun en tredjedel af arbejdstiden i byggeriet er værdiskabende” (Only a third of working hours in construction projects are value-adding), Aarhus University, Department of Engineering, 22 August 2018