Panelized and Modular Building Systems: UK vs. Global Use

Introduction and Research Framework

Housing shortages following the Second World War, rising housing demand, and an increase in defective traditionally built homes prompted the UK government to pursue sustainable housing development. The principal government aim is to improve the methods by which homes are built in the UK in order to address the housing shortage and enhance cost-effectiveness in housing production. Additionally, changing market forces coupled with evolving planning policy are pressing the house-building industry to reconsider its approach to construction. Population growth in the UK over recent decades, alongside concern for improved housing performance, has necessitated the adoption of Modern Methods of Construction (MMC) (Pan, Gibb & Dainty, 2005). MMC encompasses a range of technologies involving the assembly and/or prefabrication of housing components off-site in less time than traditional methods (the Commission for Architecture and the Built Environment, 2005).

MMC is an innovative system within the construction sector that allows house-builders to produce homes using factory-prefabricated materials in a shorter timeframe. Despite the sustainable advantages that off-site technologies have introduced into UK housing construction, the current level of housing production using off-site MMC remains generally low (Pan, Gibb & Dainty, 2005). In the UK, the majority of homes are still built using the traditional brick-and-block system. The National House Building Council estimates that only 10% of house-builders use panelized and modular building systems. By contrast, in Japan approximately 40% of new housing is built using MMC, and Scandinavian countries, Germany, and Japan all make considerably greater use of MMC for house building than the UK.

The fundamental aim of this study is to advance both industry and academic understanding of panelized and modular building systems, and to explore the key factors contributing to their low uptake in the UK. To achieve this, the study formulates research objectives designed to build greater understanding of why MMC use in the UK lags behind other countries.

Research Objectives

To investigate the factors leading to the low use of panelized and modular building systems in the UK compared to other countries, and to provide potential solutions for increasing their use in housing construction.

Research Questions

What are the leading factors behind the low use of panelized and modular building systems in the UK compared to other countries? Which countries have higher use of these systems, and what accounts for that higher use?

This study collects both primary and secondary data to answer these questions. In doing so, it gains insight into the factors behind the low use of panelized and modular building systems in the UK and contributes to the body of MMC knowledge by identifying countries with higher MMC adoption and the major factors enabling it.

Research Problem

"The UK house-building industry has often been criticized for failing to meet the housing needs of the country. The traditional craft-based build process is labour intensive with a long lead-time and is difficult to control for product quality. It is also not suitable for configurable designs that would help to customise the home, and the industry has been criticised for excessive standardisation of its products. Attempts at industrialisation, usually employing frame or panel-based build methods seen in many countries, have failed due mainly to lack of clear objectives. A change in build technology is also only one step in addressing the concerns of poor quality and lack of product variety." (Roy, Brown & Gaze, 2003, p. 137).

The impetus for using off-site technologies for house building in the UK began after the First World War, when traditional construction could not meet housing demand and there was a shortage of skilled labour. A few decades later, the success of prefabricated housing was questioned on quality grounds, and traditional housing regained its dominance. In more recent decades, however, off-site housing has seen a return of market interest. Despite this renewed trend, traditional housing still dominates the UK market and the current use of off-site MMC remains low. The high cost of materials used in off-site housing units has been identified as a major driver of this low uptake (Pan, Gibb & Dainty, 2005).

While a number of studies have explored MMC in the UK in general terms, there remains a scarcity of research examining why panelized and modular building systems specifically are used less in the UK than in other countries. This study attempts to fill that gap, providing a comprehensive investigation of the contributing factors and recommending strategies to increase the use of off-site technologies in UK house building.

Theoretical Lens

The study employs the economic theory of supply and demand to explain the general housing situation in the UK. Wilson (2010) argues that housing supply is failing to keep pace with housing demand. At the time of writing, there were approximately 1.8 million registered households on waiting lists in the UK, leading to overcrowding in private and social housing stocks. The government estimated a need for 240,000 additional homes by 2016.

Research Contribution

This study enhances understanding within the UK construction industry of the techniques needed to produce MMC homes at lower cost. It contributes to the body of knowledge on factors behind the low use of panelized and modular systems in the UK, and offers insights for policy makers on the barriers facing the construction industry and the strategies required to overcome them.

Overview of Panelized and Modular Off-Site Systems

Modern Methods of Construction (MMC) involve the use of housing components that are specially designed and manufactured in a factory off-site. There are two major product categories: panelized systems and modular systems.

Panelized Systems

Panelized products comprise ready-made walls, roofs, and floors. The panels are transported to the building site for assembly, a process that can often be completed within a single day. Some panels incorporate built-in wiring, further accelerating construction. The panelized off-site building approach can include load-bearing exterior walls and may use light-gauge steel, timber, structural insulated panels (SIPs), non-structural panels, or concrete to create the entire building envelope (Parliamentary Office of Science and Technology, 2003).

Burwood and Jess (2005) describe a more complex variant called the closed system, which involves additional factory fabrication such as insulation and lining materials. Panel types may include steel frame or timber frame, and may incorporate prefabricated load-bearing elements.

Several advantages flow from using panelized systems. Labour savings are significant because the panels are already manufactured before arriving on site. There is a marked reduction in construction time and less wastage of materials. Builders report that a watertight home can be assembled within three to four days, and occupied within 60 to 90 days. A team of construction workers supervised by a trained foreman can assemble a panelised home, and the system does not require extensive shipping clearances. Ely (2006) notes that panelized systems are pre-insulated and subject to rigorous quality control in the factory.

Despite these benefits, the panelized system is not as efficient as the modular system. It requires a high level of on-site finishing and demands considerable space during the building process (Ely, 2006).

Modular Systems

Modular off-site building technology involves structural units that are pieced together to form a completed dwelling. Modular construction is frequently used for kitchens and bathrooms, and between 80% and 90% of a modular home is typically constructed in the factory before being transported to the site for final assembly. The prefabricated modules — often called "pods" (Burwood & Jess, 2005, p. 1) — can be finished in the factory complete with mechanical and electrical wiring. Pods may be constructed using light-steel frames, timber frames, concrete superstructures, or hot-rolled steel frames (Burwood & Jess, 2005).

Modular systems offer important benefits to the housing construction sector. Designs can be produced with computer-aided design tools, with the finished design transferred directly to the factory floor. The system enables high levels of internal finishing and a high degree of quality control. It also allows for better efficiencies and improved economies of scale. Walls built to modular standards are designed to enhance energy efficiency and are stronger than traditional brick-and-block construction. Modular materials can even be used for temporary homes, since the building can be disassembled and reconstructed elsewhere. Construction time is reduced substantially: a builder can complete a home using panelized or modular methods in around 16 weeks, compared with 39 weeks using traditional brick and block.

The National Audit Office (2005) argues that labour use can be drastically reduced through panelized and modular construction, and that it is possible to build four times as many homes using the same on-site labour force. The decline in on-site labour requirements reduces overall labour costs. From the perspective of house-builders, both systems improve business efficiency and deliver quality and customer satisfaction.

Despite these benefits, the overall cost of completing a home using MMC technologies is higher than that of traditional brick-and-block construction, primarily because of the cost of manufacturing off-site components and the need to import some materials not available domestically (National Audit Office, 2005).

Notwithstanding the higher upfront cost, panelized and modular systems deliver superior housing quality and durability. A home built using a light steel frame system can have a lifespan of 200 years, meeting requirements for durability, high performance, and whole-life cost. The Parliamentary Office of Science and Technology (2003) similarly notes that MMC homes typically have fewer defects and are more energy-efficient than traditional brick-and-block homes.

The shortcomings of the modular system include the need for shipping clearances before modules can be transported to site, limited opportunity for homeowners to inspect the build during fabrication, and a requirement for skilled installation on site — particularly where materials have been imported (Ely, 2006).