Modern methods of construction (MMC) are primarily a set of innovative alternatives to traditional construction approaches. These methods are characterized by the use of novel construction practices and materials that minimize on-site labor-intensive work.1,2
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MMC can increase environmental sustainability and boost the efficiency and productivity of new housing delivery. These methods are increasingly used in construction across different structures, including high-rises, traditional housing, warehouses, and factories.1,2
MMC Overview
MMC covers a diverse range of building products and processes, including the construction of full three-dimensional (3D) modules/units in a factory setting. These include the construction of rooms, including kitchens, bathrooms, and bedrooms. They are subsequently transported to the actual construction site and integrated with the rest of the building, typically by stacking modules vertically.3
MMC also includes the construction of two-dimensional (2D), flat panels/units in a factory setting. Different material types are utilized to construct 2D panels, which are used to make roofs, floors, and walls. These are transported, assembled, and integrated with other building parts.3
Advantages
MMC reduces waste generation during the construction process, ensures consistent quality, and improves the overall construction process. Faster construction project delivery can be achieved as these methods speed up construction by 20-60%. Several construction processes happen in factory conditions/offsite where factors like bad weather do not disrupt the delivery times, leading to faster project completion and improvements in both on-site and off-site activities.2
High-quality homes can be built as MMC promotes accuracy through stringent quality-control processes and digitalization. The creation of construction units and components using factory standard consistency and precision significantly contributes to the structures’ quality. Thus, the structure could effectively realize the intended durability and performance requirements.2
Additionally, MMC strengthens the construction quality, such as by enhancing air-tightness in homes, for increased sustainability. The improved air-tightness in homes promotes higher building energy ratings and enhances their energy performance, leading to reduced carbon emissions, lower energy bills, and improved comfort.2
MMC also reduces energy demand and manufacturing waste, improves circularity through the most efficient use of materials, and decreases embodied carbon by encouraging the utilization of lower carbon-intensive materials. Moreover, MMC reduces construction costs when they are integrated with a steady standardized design supply, which increases the affordability of new housing for the tenant/purchaser.2
Workforce diversity can be achieved using MMC as an indoor factory environment, coupled with a consistent place of work and regular working hours, attracts a more localized and diverse workforce.2
Classification
MMC can be classified into off-site and near-site pre-manufacturing-led approaches and site-based process improvement-led approaches. Off-site and near-site pre-manufacturing-led approaches include pre-manufacturing of 2D primary structural systems (panelized construction), 3D primary structural systems (volumetric construction), non-structural assemblies and sub-assemblies, non-systemized structural components, and additive manufacturing of structural and non-structural components.2,4
The site-based process improvement-led approaches include site process-led labor reduction and productivity assurance improvements (innovative processes and approaches) and traditional building product-led site labor reduction and productivity improvements.2,4
Among these approaches, site process-led labor reduction and productivity assurance improvements and pre-manufacturing of non-structural assemblies and sub-assemblies, 2D primary structural systems, and 3D primary structural systems are the most commonly used MMC.2
Volumetric housing units are 3D units/modules fabricated in controlled environments/factories and then delivered to the actual construction site for assembling and installation. The level of finish of these units varies from a basic structure to a structure with all services installed.2
Additionally, this category includes structural framing with roofing and comes with/without internal fit-out such as bathrooms and kitchens, and with/without cladding, which is an external surface that protects buildings. A building can be constructed by combining multiple volumetric units, or a single volumetric unit can be used as a small dwelling.2
Moreover, these units can be combined with other construction forms like pre-manufactured roofs or bathroom units.2 Open panels are more common and form only the skeletal structure, while closed panels are more sophisticated and include electrical services, insulation, and lining materials.3
Cross-laminated timber, insulated concrete formwork, structurally insulated panels, precast concrete, light gauge steel frame/light steel, and timber are used in 2D panelized components.3 Innovative site processes and approaches use novel construction techniques that improve the on-site processes.2
Examples of this category include virtual models of buildings, weatherproofing, and standardized works like insulated concrete formwork. Additionally, technologies such as virtual and augmented reality are used to visualize final and planned works.2
Digital tools like drones, robotics, and driverless cranes and diggers are also utilized in this approach. Additive manufacturing/3D printing is used to create construction components like walls, structural elements, and even entire buildings.2
Challenges in MMC
The design of the structures must be finalized in advance of the site-build in much more detail, which is a major challenge of off-site manufacturing (OSM). However, OSM requires a much shorter duration for the site-build phase compared to traditional construction when the total project period for build and design is considered.4
Additionally, the dependence on one supplier is another significant challenge as delays and additional expenses could affect the construction projects if a supplier fails to fulfill their obligations. Functional adaptability and future maintenance are also potential concerns for off-site manufactured buildings.4
Several composite materials that are used in MMC projects cannot be easily recycled/reused at the building’s end-of-the-life. This will negatively contribute to a life-cycle analysis of a project’s environmental impacts and benefits.4
Moreover, good detailed and conceptual design, careful construction detailing, and proper choice of system in the early stages of a project are crucial as OSM processes alone do not ensure quality.4
Several barriers are also hindering the implementation of MMC in different countries. For instance, in a paper recently published in the Journal of Civil Engineering Research and Technology, researchers identified the most significant barriers to MMC implementation, which included supply chain disruptions, an emerging MMC market, transportation challenges, high initial costs, and inadequate government support.5
Future Outlook and Conclusion
One of the biggest advantages of MMC is its significant contribution to sustainable construction. The future of MMC looks bright with key players such as AECOM, Saint-Gobain, Skanska, and Siemens AG driving the market by adopting sustainable building practices and focusing on innovation. Additionally, several leading companies, including Morgan Sindall Construction and Balfour Beatty, have already adopted MMC to improve project efficiency and create sustainable and innovative structures.6,7
The United Kingdom (UK) government and industry leaders published the Construction 2025 Strategy with a vision of changing the industry using four targets, including the import/export trade gap, level of greenhouse gas emissions, operational cost, and reduction in construction project duration.8
A paper recently published in the Ain Shams Engineering Journal showed that MMC could help in realizing those construction 2025 targets, with a similarity index ranking displaying that MMC would be most effective for achieving trade and greenhouse gas emission targets.8
In summary, MMC offers numerous benefits, including increased sustainability, efficiency, and productivity. However, challenges such as supply chain disruptions and high initial costs must be addressed to fully realize its potential.
References and Further Reading
- Modern methods of construction [Online] Available at https://www.istructe.org/resources/design-and-construction/mmc/ (Accessed on 24 September 2024)
- Modern Methods of Construction Introductory Guide [Online] Available at https://www.gov.ie/en/publication/e5e78-modern-methods-of-construction-introductory-guide/ (Accessed on 24 September 2024)
- Modern Methods of Construction: barriers and benefits for Irish Housing [Online] Available at https://www.ciob.org/industry/policy-research/MMC-Ireland (Accessed on 24 September 2024)
- Modern methods of construction (MMC) - A long and ongoing journey! [Online] Available at https://www.istructe.org/resources/blog/modern-methods-of-construction-(mmc)-a-long-and-on/ (Accessed on 24 September 2024)
- Layon, L.B., Siyabi, M.S.A.A., Garcia, A.R.M., Umar, A.A. (2024). Barriers Affecting the Implementation of Modern Methods of Construction (MMC) in Oman. Journal of Civil Engineering Research & Technology. https://www.onlinescientificresearch.com/abstract/barriers-affecting-the-implementation-of-modern-methods-of-construction-mmc-in-oman-4588.html
- Offsite and Modern Methods of Construction (MMC) [Online] Available at https://www.morgansindallconstruction.com/our-approach/modern-methods-of-construction-mmc/ (Accessed on 24 September 2024)
- Accelerating the use of Modern Methods of Construction [Online] Available at https://www.balfourbeatty.com/media-centre/latest/accelerating-the-use-of-modern-methods-of-construction/ (Accessed on 24 September 2024)
- Maqbool, R., Namaghi, J. R., Rashid, Y., Altuwaim, A. (2023). How modern methods of construction would support to meet the sustainable construction 2025 targets, the answer is still unclear. Ain Shams Engineering Journal, 14(4), 101943. DOI: 10.1016/j.asej.2022.101943, https://www.sciencedirect.com/science/article/pii/S2090447922002544
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