Off-site Construction Methods Research Articles

Building an Information Modeling-Based System for Automatically Generating the Assembly Sequence of Precast Concrete Components Using a Genetic Algorithm

Facing a significant decrease in economic working processes, Off-Site Construction (OSC) methods have been frequently adopted in response to challenges such as declining productivity and labor shortages in the construction industry. Currently, in most OSC applications, the assembly phase is traditionally managed based on the personal experience and judgment of the site managers. This approach can lead to inaccuracies or omissions, particularly when dealing with a large amount of information on large, complex construction sites. Additionally, there are limitations in exploring more efficient and productive alternatives for rapidly adapting to changing on-site conditions. Given that the assembly phase significantly affects the OSC productivity, a systematic management approach is crucial for expanding OSC methods. Some initial studies used computer algorithms to determine the optimal assembly sequences. However, these studies often focused on geometrical characteristics, such as component weight or spatial occupancy, neglecting crucial factors in actual site planning, such as the work radius and component installation status. Moreover, these studies tended to prioritize the generation of initial assembly sequences rather than providing alternatives for adapting to evolving on-site conditions. In response to these limitations, this study presents a systematic framework utilizing a Building Information Modeling (BIM)–Genetic Algorithm (GA) approach to generate Precast Concrete (PC) component installation sequences. The developed system employs Genetic Algorithms to objectively explore diverse assembly plans, emphasizing the flexibility of accommodating evolving on-site conditions. Real on-site scenarios were simulated using this framework to explore multiple assembly plan alternatives and validate their applicability. Comprehensive interviews were conducted to validate the research and confirm the system’s potential contributions, especially at just-in-time-focused PC sites. Acknowledging a broader range of variables such as equipment and manpower, this study anticipates fostering more systematic on-site management within the context of a digitized construction environment. The proposed algorithm contributes to improving both productivity and sustainability of the construction industry by optimizing the management process of the off-site construction projects.

STUDENT MADE INFRASTRUCTURE IN RURAL CONTEXTS - LA ESTRELLA STEEPLE DESIGN BUILD PROJECT

The Design/Build Methodology in the Education of Architecture is an alternative to traditional and theoretical training where real projects and construction takes place. This paper focuses on a case study from the School of Architecture course “Introducción a la Construcción” at the Pontificia Universidad Católica de Chile. Its main feature is exploration on timber construction through a direct hands-on experience and development of prefabricated built projects. Timber has been used as the predominant building material since it allows to explore concepts of prefabrication, modular coordination, and structural performance. This intuitive design approach is complemented by a low-tech and low-cost solution according to the local context. Recently the course has realigned its focus to community-oriented projects outside the university in a process that entails complex management and technical issues. The project considers a steeple structure commissioned by La Estrella parish and the impact of project´s brief constraints on the timber structure in terms of: design and prefabrication process: brief constraints plus available design tools were applied to on-site and off-site construction methods to allow quick assembly. A participative and iterative process through design and testing of different timber structural components developed by groups of students; management issues: communication, consultants and construction management by the academic staff and students; relationship with community: this process includes participatory design, community engagement and participation. Conclusions drawn from this project show a successful experience of timber building systems applied to this methodology. Built results have exceeded original expectations while the engagement between the student project and the benefiting community constitute a successful experience in the exploration of these teaching strategies. Involvement of students in management process is an aspect that needs further development as a relevant feature to be considered on future off-campus projects.

A Novel Offsite Construction Method for Social Housing in Emerging Economies for Low Cost and Reduced Environmental Impact

Offsite construction methods have shown many advantages over traditional construction techniques, especially related to efficiency and productivity during the construction phase. Nevertheless, offsite construction generally involves oversizing the internal structure of the modules due to the internal stresses produced during transport and lifting operations, producing an increase in material usage, direct cost, and carbon footprint. In developing countries, the direct cost of social housing is the most important factor determining the feasibility of construction. For this reason, oversizing the internal structure of the modules can play an important role in the adoption of a modern construction technique such as offsite construction systems. In order to solve this issue, a temporary reusable stiffener structure is proposed to allow an economical offsite construction system using a lightweight steel framing structure used in traditional methods. The reusable structure was designed using a finite element method, and the direct cost and carbon footprint of the structure were evaluated. The results show that the proposed construction strategy allows for a low cost and reduced environmental impact due to a lower usage of materials in the modules and the possibility of a circular economy approach to the reusable structure.

Identification and Evaluation of the Key Decision Support Factors for Selecting Off-site Construction in Canada: A Building Information Modeling (BIM)-enabled Approach

The construction industry lags behind other sectors in terms of productivity performance, with many megaprojects experiencing cost overruns. While there are various reasons for this, the most significant one is the lack of efficiency. Adopting the off-site construction (OSC) methodology can improve productivity by enhancing project efficiency mainly in terms of time, cost and quality. Although OSC, off-site manufacturing (OSM), Industrialized Building System (IBS), prefabrication, modular, or other similar terms are not novel concepts, it is essential to shift any aspect of construction project activity from traditional onsite methods to a controlled, factory-based and manufacturing concept of production. Industrialization and digital fabrication have gained significant prominence in recent years, as they are perceived as a viable solution to the issues faced by the construction sector. As OSC is gradually gaining interest in building projects, it is crucial to identify and validate the key decision support factors (KDSFs) for selecting an appropriate OSC method from the early design stage. The purpose of this study is to identify, verify, and evaluate the KDSF for selecting OSC in Canada. This study utilized a mixed-methods design, comprising a systematic literature review (SLR) and pilot expert reviews through semi-structured interviews and surveys, to accomplish the research objectives and ensure the validity and reliability of the findings. Twelve interviews were conducted to validate and analyze the KDSFs, which were then prioritized using the mean score (MS) analysis and weighting function. Based on the research methodology, 32 KDSFs were validated and grouped into 7 'dimensions'. Further analysis concluded that the most important 'dimension' in selecting OSC for a building project in Canada is project time which consists of the design period, production time, mobilization and transfer time, as well as the assembly, and construction periods.

High-performance grout-reinforced shear connectors for hybrid steel-cross-laminated timber building systems: Experimental study

Wood-based construction advancements have been observed recently with the adoption of hybrid assembly and offsite construction methods, relying on prefabricated components, such as volumetric cross-laminated timber (CLT) modules or composite panel-type wall and floor elements. Within the high-rise timber building framework, mass timber structural assembly requires connections designed to accommodate innovative technologies to limit damage under seismic loads and mitigate lateral vibration of the building under serviceability loads. As part of the performance-based capacity and constructability enhancements, current research efforts have been on the development of high-performance and reliable mass timber connections. This paper presents a new connection design method for hybrid steel-CLT composites and assemblies. Shear connectors are fabricated by encasing steel rods into CLT panels using an epoxy-based grout, with geometry specified to provide stiffness and shear capacity target levels. An insight into their behaviour and performance is given based on an experimental dataset comprising 240 full-scale push-out shear tests and an array of rod diameter, grout thickness, and mechanical properties of steel and CLT. Maximum shear strength of 289.6 kN and elastic stiffness of 243.2 kN/mm were attained for the tested specimens, showing that strong and stiff behaviour were attainable. Elastic mechanical properties of connectors were shown to be governed by the rod diameter, whereas strength resistance and failure mode from the grout thickness, allowing for decoupling of design parameters and fine-tuned design. The yield point was shown clearly identifiable, supporting optimum capacity design strategies. Observed failure modes were mostly ductile and with a maximum slip ductility of 6.4, and on average comparable with common wood bolted connections. A resistance factor of 0.8 was shown adequate to design the shear connectors using the calculated 5th percentile values of the yield shear resistance and maximum shear resistance, relatively, for elastic and plastic design strategies. Large-scale building applications were shown attainable by intrinsic individual mechanical properties of the connector, supporting deconstruction and reuse of the hybrid steel-timber structural system components when the connector is capacity-protected and behaves elastically; thus, designed using its 5th percentile yield shear strength.

A framework for the evaluation of the decision between onsite and offsite construction using life cycle analysis (LCA) concepts and system dynamics modeling

The decision to choose between onsite and offsite construction is important in the effort toward sustainable construction. Offsite construction is often promoted as an environmentally friendly approach to construction operations. However, previous studies have shown that there is a lack of clarity on the environmental trade-offs between onsite and offsite construction. Factors that can affect the decision to build onsite or offsite include the availability of a local offsite manufacturing facility, the distance of the offsite factory to the final place of use, the proximity of the site to the local supply of material and labor, etc. This study provides a framework to apply the system dynamic modeling technique to evaluate how various factors can affect the environmental impact of the building construction phase (for onsite or offsite construction methods). The system dynamic model (using Vensim software) that was developed provides a platform that allows users to input variables such as the distance that is expected for transportation of labor, material, and equipment to both the onsite facility and the offsite construction location, factors associated with the use of equipment for construction, the distance needed for transportation of building panels or modules from the offsite facility to the final site, etc. Among other things, the model showed that an increase in the distance from the offsite yard to the final construction site increases the total impacts of transportation of completed modules. An increase in the number of trips for the transportation of material to the onsite construction location increases the total impact of onsite construction. In terms of the environmental impact of construction, none of the two methods of construction gives an absolute superiority over the other. The environmental performance of offsite and onsite depends on various associated factors. It is recommended that building practitioners review various factors that are peculiar to their projects to make an informed decision on the best construction methods.

Offsite Construction Methods—What We Learned from the UK Housing Sector

Offsite construction has become popular in recent times due to the numerous benefits it offers compared to traditional construction methods. This paper explores the different offsite construction methods, the motivations for adopting these approaches, and the cost-effectiveness of these methods in the UK housing sector using multiple case studies. Firstly, the literature and data were obtained from various sources including professional body reports, industry reports, government websites, and journal articles. Following the review, twelve completed housing projects from the UK which used offsite construction approaches were analyzed. The review of these projects showed that different offsite methods were used in these projects. These include Structural Insulated Panels (SIPs), Timber Frames, Precast Concrete, Steel Frames, Volumetric Construction, Gyproc Habito Plasterboards, and Light Gauge Steel (LGS) technology. The key motivations for adopting offsite construction in these projects include the speed of construction, durability of the products, aesthetic considerations, thermal quality, low air leakage requirements, and quality of construction. Of the 12 cases, only two recorded a higher cost for the offsite construction method compared with the alternative using traditional approaches. The outputs of this paper provide evidence-based strategies which would inform practitioners on the best practices for adopting offsite construction methods and what to expect.

Potential of Modular Offsite Construction for Emergency Situations: A New Zealand Study

Natural disasters cause significant adverse social and financial impacts by damaging homes and infrastructure. These disasters also need a quick and immediate solution to post-disaster housing problems, to provide temporary housing services for short-term disaster relief and reconstruction of lost and damaged houses for complete recovery. Reconstruction of new permanent housing for disaster victims is one of the most time-consuming post-disaster activities. However, time is a vital consideration that should be minimized for the reconstruction of houses for affected populations. Modular offsite construction technology has the potential to enhance the post-disaster housing reconstruction process due to its intrinsic characteristics of time-efficiency. This study aimed to assess the potential of the modular offsite construction method as an approach that could promote the design and construction process of post-disaster reconstruction in New Zealand in emergencies. An extensive literature review has been carried out to evaluate the features of the modular construction method, which can add value to the post-disaster recovery phase. To evaluate the suitability and viability of modular offsite construction for post-disaster reconstruction and to find substantial obstacles to its implementation, feedback was collected and evaluated using the multi-attribute methodological approach by performing a national survey of construction industry experts in New Zealand. Semi-structured interviews with New Zealand experts were then followed to confirm and validate the questionnaire findings. The findings indicate that modular offsite construction technology is a viable solution for providing housing in emergencies or during post-disaster reconstruction in New Zealand, with its time-efficiency and ability to overcome the challenges of the current traditional method by its specific advantages. Reduced need for onsite labor, overcoming local labor resource constraints affected by the disaster, and enhanced productivity due to a controlled environment are the advantages of the modular offsite technology, which are discussed in this research.

Mapping activities and inputs of modular construction with steel 3D modules in Brazil

COVID-19 has intensified the need for faster and more efficient construction in Brazil. In this regard, offsite construction methods are important, in particular, modular construction with steel 3D modules. While extensively discussed in the literature, details, such as the inputs of the process related to modular construction, are rarely provided. The purpose of this paper is to map the process involved in modular construction with steel 3D modules, including the operations and inputs. To this end, based on a literature framework, a case study was performed considering six cases of modular construction with steel 3D modules carried out by three different companies. As a result, the process is described in a flowchart, composed by six stages: 1) design and planning; 2) substructure execution; 3) production of the modules; 4) transport of the modules; 5) assembly; and 6) installation. This study shows that the fundamental steps involved in the production of the modules are uniform among the construction projects studied. However, the customization and, consequently, the inputs used to produce the modules vary greatly. Thus, this paper contributes to structuring and documenting the process involved in modular construction with steel 3D modules, including the operations and inputs.

Life cycle sustainability assessment for modular construction – A proposed conceptual framework

Offsite construction (OSC) is increasingly recognised as a viable alternative for conventional in-situ construction. Modular construction (MC) is one of the most advanced and efficient OSC methods in the construction industry. Even with the distinctive benefits offered by MC, it is imperative to investigate the sustainability performance of MC to understand the trade-offs with traditional construction. Life cycle sustainability assessment (LCSA) is a tool that integrates the three pillars of sustainability from a life cycle perspective. At present, the most common method is to consider the LCSA as a sum of life cycle assessment (LCA), life cycle costing (LCC), and social LCA (S-LCA). However, studies that have employed the LCSA methodology in assessing MC are still lacking in the literature. Relevant literature still lacks comprehensive framework guidance to conduct LCSA of MC. Thus, this paper aims to propose a conceptual framework that integrates the triple bottom line (TBL) of sustainability to assess the sustainability performance of MC using LCSA. The publications acquired from the keyword search analysis were reviewed to develop the conceptual framework by identifying the key factors and challenges to the LCSA. The framework integrates the methodological steps, findings, and gaps related to LCSA discovered from the literature survey. The results show that the LCSA goal and scope should be defined properly to address the complications from the methodological differences of the TBL of sustainability. The proposed framework offers insight to academia and construction industry practitioners about the holistic investigation of the sustainability performance of MC.

BIM-Based Management System for Off-Site Construction Projects

Offsite construction (OSC) is one of the alternative methods for the various challenges that the construction sector faces today. This study developed a management system based on building information modeling (BIM) to execute OSC projects successfully. Because OSC differs from the conventional onsite building method, the authors studied and analyzed several project cases and interviewed the participants and stakeholders. The OSC method has unique characteristics in the aspects of the projects’ location and time, production process, flow, method, facility, and environment. Moreover, before the system development, we analyzed the OSC project management, usability, and system requirements. These requirements were turned into a BIM-based system following a waterfall model, with six management menus: drawing, schedule, production, logistics, installation and progress monitoring, and progress payment. This study implemented each menu’s vital functions within the system more effectively due to the BIM-based technological features, such as object-oriented data processing, visualization, high interoperability, linkage, and integration. The developed system was applied to four projects. The test resulted in a streamlined work process, improved activity, and less input time and workload than in a non-BIM-based management environment. These findings indicated that the proposed BIM-based system enabled OSC project management to perform better.

Requirements Analysis for Development of Off-Site Construction Project Management System: Focusing on Precast Concrete Construction

There has been increasing interest in the off-site construction (OSC) method in response to issues such as stagnant labor productivity, shortage of skilled workers, challenging site management, heightened safety and health-related regulations, and the push for carbon neutrality. Although efficient performance of an OSC project requires development of management techniques, and application of a management system that reflects the characteristics of the OSC projects, related technologies remain in their infancy. In this study, targeting precast concrete (PC) construction, which is one of the representative construction types of the OSC method, we derive the characteristics of OSC project management in six aspects: production place and time, production process, production method of construction, production method, production entity and facilities, and production environment. Based on this result, we further derived the requirements for developing an OSC project management system. Furthermore, based on the derived requirements, we constructed a system development scenario for the establishment of an installation plan and shipment requests. The managerial characteristics and requirements of the OSC project, presented in this study, provide the theoretical basis for developing OSC project management techniques, as well as guidance for the development of the OSC project management system in the future.

Process evaluation of construction methods to quantify safety

The use of off-site construction methods is increasing within the construction industry. While this method has been captured by a variety of terms, they all refer to the process of producing project components in a manufacturing-like facility off-site and transporting completed units to site to be assembled to achieve the desired end-product. To support the quantification of safety performance in off-site construction versus conventional on-site methods, the research has developed a generalized model for capturing and evaluating construction methods. The methodology was developed in partnership with local practitioners to define, assess and compare on-site and off-site construction practices with a safety lens, and the methodology is partially validated in collaboration with various project owners to assess case study projects that employed off-site construction into their processes. The evaluation methodology takes a construction product-focused approach with emphasis on defining a complete material supply chain and capturing the data needed to support quantifiable safety evaluations of the process. As such, the approach takes a unique approach to establish an evaluation methodology for future comparisons.

Selecting a Suitable Sustainable Construction Method for Australian High-Rise Building: A Multi-Criteria Analysis

The evolution of innovative construction technology and automation has rapidly transformed the construction industry over the last few decades. However, selecting the most efficient and sustainable construction technology for high-rise building construction is a critical factor in completing the project successfully. This requires a multiple-judgment-decision process relevant to cost, time, environment, sustainability, quality, etc. Thus, this research aims to identify the most suitable sustainable construction method for high-rise building construction in Australia. Three construction methods (i.e., automated building construction, aluminium formwork construction, and off-site construction) and robotic construction technology are reviewed in terms of economic, equity and environmental performance. A detailed multi-criteria analysis is conducted concerning the weighting calculated for each construction method, which aids in recommending a sustainable and cost-effective method. The analytical hierarchy process (AHP) is used as a multi-attribute decision-making tool to determine the weighting factors. The results show that the off-site construction method and robotic construction technique significantly improve the construction performance of high-rise construction in Australia. However, the finding is based on data obtained from a limited number of experts. Thus, a detailed case study with a greater number of expert opinions is needed to ensure the significance of the finding. However, the AHP-based approach method can be used to select sustainable construction alternatives for high-rise buildings.

Barriers to innovation in the housing sector: Economic justifiability of offsite construction for housebuilders

The uptake of offsite construction in the housing sector is low, despite extensive discussions on its benefits. Offsite construction methods significantly disrupt the products and processes of the housing sector. In this context, the interactions of autonomous actors in a loosely coupled system within and beyond the industry determines desirability of offsite construction methods for different actors and consequently the uptake of the methods on sector level. As a result, there is a need to systematically synthesise the mechanisms that shape the desirability of offsite construction for industry practitioners. To fill this gap, a qualitative system dynamics model is developed in this research to study the feedback mechanisms that encourage/discourage application of offsite construction methods with a focus on economic justifiability of these methods for housebuilders. The model is developed via a grounded theory-based approach through a synthesis of the literature. A series of semi-structured interviews with industry experts are then carried out to verify and contextualise the model. The results indicate that a long-term holistic perspective accounting for the interactions of different actors can redefine economic justifiability and consequently improve desirability of offsite construction methods for builders, which will then feed back into the system to sustain the long-term benefits of all involved actors. The model is used to propose uptake strategies based on strengthening the feedback structures that reinforce economic justifiability of offsite construction methods and weakening those that decrease economic justifiability.

Economic sustainability benchmarking of modular homes: A life cycle thinking approach

Sustainable built environment has been of interest to many stakeholders in the recent years. However, life cycle economic performance as one of the key dimensions of sustainability has not been sufficiently investigated for buildings constructed using off-site construction methods such as modular construction. This research has proposed a framework to benchmark the life cycle economic sustainability of single-family modular homes. First, suitable economic performance criteria were selected and suitable measurable economic performance indicators were developed under each criterion. A performance level function was established for each indicator by which all indicators can be calculated and presented by a normalized performance level that enables combining quantitative and qualitative indicators. Subsequently, a multi-criteria decision analysis-based methodology was employed to develop a set of economic sustainability indices at the criteria level and also at the overall economic sustainability performance level. To compare and contrast the developed indices of a given modular building with the performance of similar conventional buildings, suitable performance benchmarks scales were established using the data of the historical economic performances of conventional homes. To examine the application of the proposed framework, two case study modular homes in British Columbia, Canada were analyzed. The results showed that both benchmarking homes performed ‘Excellent’ with respect to the overall economic sustainability. However, improvements are required to enhance the economic performance with respect to a number of criteria. The proposed framework can assist the construction decision makers, developers, and contractors with making informed decisions on the selection of the construction method. Furthermore, it can be used to address the underperforming areas over the life cycle of a modular building, even if the decision on the construction method has already been made.

Simulation-Optimization for the Planning of Off-Site Construction Projects: A Comparative Study of Recent Swarm Intelligence Metaheuristics

Off-site construction is a modern construction method that brings many sustainability merits to the built environment. However, the sub-optimal planning decisions (e.g., resource allocation, logistics and overtime planning decisions) of off-site construction projects can easily wipe away their sustainability merits. Therefore, simulation modelling—an efficient tool to consider the complexity and uncertainty of these projects—is integrated with metaheuristics, developing a simulation-optimization model to find the best possible planning decisions. Recent swarm intelligence metaheuristics have been used to solve various complex optimization problems. However, their potential for solving the simulation-optimization problems of construction projects has not been investigated. This research contributes by investigating the status-quo of simulation-optimization models in the construction field and comparing the performance of five recent swarm intelligence metaheuristics to solve the stochastic time–cost trade-off problem with the aid of parallel computing and a variance reduction technique to reduce the computation time. These five metaheuristics include the firefly algorithm, grey wolf optimization, the whale optimization algorithm, the salp swarm algorithm, and one improved version of the well-known bat algorithm. The literature analysis of the simulation-optimization models in the construction field shows that: (1) discrete-event simulation is the most-used simulation method in these models, (2) most studies applied genetic algorithms, and (3) very few studies used computation time reduction techniques, although the simulation-optimization models are computationally expensive. The five selected swarm intelligence metaheuristics were applied to a case study of a bridge deck construction project using the off-site construction method. The results further show that grey wolf optimization and the improved bat algorithm are superior to the firefly, whale optimization, and salp swarm algorithms in terms of the obtained solutions’ quality and convergence behaviour. Finally, the use of parallel computing and a variance reduction technique reduces the average computation time of the simulation-optimization models by about 87.0%. This study is a step towards the optimum planning of off-site construction projects in order to maintain their sustainability advantages.

Assessing off-site readiness in construction organisations: cases from India

PurposeThis paper aims to present factors affecting the Indian construction organisations in adopting off-site construction (OSC) methods.Design/methodology/approachAn existing readiness maturity model has been used to assess three large organisations in different parts of India. A case study methodology has been adopted in this paper to highlight critical issues in OSC adoption in India.FindingsThis paper presents three case studies and concludes the Indian construction sectors readiness to adopt the OSC methods. Through the case studies, different issues related to the adoption of OSC have been identified and highlighted for the Indian construction sector. Although the three companies are large, there are several small- and medium-sized enterprises (SME) operating in India's construction sector, and future research shall be needed to review these SMEs.Research limitations/implicationsThis research study is broadly focused on developing and assessing an OSC readiness framework for Indian construction organisations. The research scope and the population for data collection are limited to large construction organisations in India only.Practical implicationsThe proposed OSC readiness maturity model guides construction practitioners in India through a structured process to assess their OSC readiness in the market. This assessment enables them to evaluate and benchmark their processes through the strategic and operational phases. This research will add to the existing knowledge of OSC in India by mapping issues relevant to India's construction industry. The research has provided background on the status of OSC, the drivers and barriers affecting the implementation of OSC techniques in the Indian construction industry.Originality/valueThrough the three case studies, several factors related to the implementation of OSC methods have been identified and highlighted within the Indian construction sector. Although the model has been applied to the Indian construction sector, it can easily be modified to fit into other areas and similar dynamics and business conditions.

Offsite construction supply chain strategies for matching affordable rental housing demand: A system dynamics approach

Australian housing affordability is influenced by both housing supply and demand factors. These factors include lengthy construction and planning process. The affordability crisis affects the housing rental sector, which accommodates more than 20 % of Australian household. This research developed a system dynamics model to simulate demography-linked affordable rental housing demand and supply in South East Queensland (SEQ). A Prefabricated Offsite Construction (OSC) housing supply strategy is compared with a traditional building approach (BAU) to investigate the effectiveness of OSC techniques to reduce informational asymmetries during development planning stages to deliver better affordable rental housing is linked to housing needs in SEQ. The model focuses on demographic groups housing demand of one, two- and three-bedroom apartment units and examines how reductions in the development process, through OSC methods, influence the efficiency of Government supported affordable rental housing supply schemes. Overall, the study finds that reduced planning and construction timeframes through OSC methods may improve demography-linked rental housing supply by approximately 6.6 % overall compared to BAU in SEQ. For 1,2- and 3-bedroom apartment demand, OSC strategies are expected to improve supply efficiency by 8.7 %, 8.4 % and 9.2 %, respectively. Optimal OSC strategies were assessed and found that flexibility in development sizes have an outsized positive effect. The study has implications for Government supported affordable rental housing strategies, including the build to rent sector.

Effects of policy on developer's implementation of off-site construction: The mediating role of the market environment

Off-site construction as an industrialized construction method has become a hot topic in addressing climate change. Government policies have been formulated to promote the development of off-site construction in China. Previous studies have found policy benefits for the development of off-site construction, but few studies have explored its effects on decision-making developers' adoption of off-site construction. This study aims to quantitatively verify the effect of policy on developer's implementation of off-site construction and to explore practical paths for encouraging developers to implement off-site construction using partial least-squares path analysis. The results show that environmental policies have significant direct effects on developer's implementation of off-site construction. In contrast, demand-side and supply-side policies only indirectly affect developer's implementation of off-site construction through their effects on the market environment. Moreover, the market environment's mediating role was verified, suggesting that the market environment should be fostered to improve developer to adopt off-site construction method and then promote off-site construction development. Furthermore, this study explored ways to stimulate developer's implementation of off-site construction through environmental policy instruments by unpacking the market environment's mediating effect.