Acta Structilia

Guidelines for resolving safety constraints using the Last Planner System in Zimbabwean construction projects

Cynthia Moyo, Fidelis Emuze, John Smallwood — Mon, 29 Jun 2026 00:00:00 +0000

Construction projects in Zimbabwe continue to experience performance challenges arising from persistent safety constraints. This study examines how the Last Planner System (LPS), a key Lean Construction tool, can be applied to reduce these safety-related barriers. The aim is to provide construction stakeholders with practical, evidence-based guidelines for implementing LPS to improve safety performance on project sites. A quantitative survey was conducted among contractors registered with the Construction Industry Federation of Zimbabwe (CIFOZ), yielding 130 valid responses. Data analysis employed descriptive statistics, mean score analysis, exploratory factor analysis (EFA), and partial least squares structural equation modelling (PLS-SEM). Results show that LPS significantly alleviates two major categories of safety constraints, namely technical and managerial inadequacies, and employee-related and project delivery concerns, supported by p-values below 0.05 and path coefficients of 0.409 and 0.520, respectively. From these findings, practical LPS implementation guidelines are proposed. It emphasises multilevel planning (master, phase, look-ahead, and weekly), systematic identification and mitigation of safety risks, enhanced worker participation to strengthen ownership of safety practices, and improved workflow reliability to prevent last-minute changes that commonly lead to accidents. Although the study is limited to Zimbabwean projects and relies primarily on quantitative data, it demonstrates that LPS offers a viable and impactful strategy for improving construction site safety. Broader adoption of LPS can support performance enhancement across the sector and aligns with Sustainable Development Goals 9 and 11.

Integrating multi-objective optimisation and life-cycle assessment in early-stage building design

Mark Alegbe, John Kalu, Laurence Chukwuemeka — Mon, 29 Jun 2026 00:00:00 +0000

The built environment is responsible for roughly 40% of global carbon emissions, compelling the need for targeted strategies that address impacts across the building life cycle. Early-stage building design still lacks integrated optimisation frameworks that quantify how material choices and envelope configurations influence life-cycle emissions and thermal comfort. This gap is critical in tropical climates, where the interaction between thermal mass, envelope performance, and operational loads is complex. Each stage of a building’s life cycle generates different carbon profiles. Designers often rely on single-metric assessments, leading to design decisions that appear sustainable but perform poorly across the full life cycle. This study develops a combined multi-objective optimisation (MOO) and life-cycle assessment (LCA) method to evaluate and balance these competing objectives across alternative design scenarios. A DesignBuilder (V6) MOO algorithm was applied to an existing tropical case building constructed with sandcrete blocks. Two optimised substitutes were developed: one combining burnt brick external walls with a clay slate roof, and another with burnt brick external walls with a green roof. Preliminary simulations show that, although material substitution reduced embodied carbon, it increased operational carbon and worsened thermal discomfort. The optimisation processes generated 626 iterations and yielded 57 non-dominated solutions, with Pareto front analyses revealing a complex interplay between design variables and performance outcomes. Subsequent LCA of the buildings using OneClick LCA revealed that horizontal structural elements accounted for up to 89% of embodied carbon in the A1-A3 (materials) stages. While embodied carbon represented 19% of total life-cycle emissions in the case building, operational carbon dominated overall impacts, reaching 87% in the second optimised building. The study concludes that Pareto-based multi-objective optimisation presents a robust framework for navigating conflicting design goals. However, it must be integrated with life-cycle evaluation to identify design interventions that can deliver the greatest environmental and thermal performance gains.

A multidimensional analysis of organisational performance drivers among local construction contractors in Kenya

Shadrack Mutungi Simon — Mon, 29 Jun 2026 00:00:00 +0000

This study investigates the influence of ten organisational determinants on ten dimensions of performance among local contractors in Kenya’s construction sector. Grounded in the Resource-Based View and Contingency Theory, the research adopts a multidimensional framework to assess profitability, growth, technical capability, business efficiency, employee satisfaction, financial stability, client satisfaction, product quality, managerial capability, and safety performance. Data were collected from 378 valid responses, using structured questionnaires administered to contractors and consultants. Multiple regression analysis was employed to model the relationships between each performance dimension and the ten determinants, culminating in a composite model of overall organisational performance. Findings reveal that strategic planning, contractor innovativeness, supplier effectiveness, organisational structure, and quality of service are the most consistent and significant predictors across performance dimensions. The composite model yielded an adjusted R² of 0.819, indicating strong explanatory power. External factors such as government support and competition showed limited but context-specific influence, while performance measurement practices exhibited paradoxical effects. The study underscores the primacy of internal strategic and operational capabilities in driving performance and offers actionable recommendations for contractors, policymakers, and industry stakeholders. These include strengthening planning systems, supporting innovation, optimising supplier networks, and reforming performance measurement frameworks to support strategic learning and continuous improvement.

Strategies for SME contractors to enhance on-site labour productivity through sustainable construction project delivery

Yongama Mtshakaza, Athenkosi Sogaxa, Justus Agumba — Mon, 29 Jun 2026 00:00:00 +0000

On-site labour productivity is a critical determinant of project performance for small and medium‑sized enterprise (SME) contractors, who play an important role in South Africa’s economic development and employment creation. Many construction projects continue to incur productivity losses, due to inadequate site management practices, skills shortages, ineffective supervision, and material supply disruptions. This study examines strategies to enhance on-site labour productivity among SME contractors within the context of sustainable construction project delivery. A quantitative research design was used, and data was collected through survey questionnaires from 155 site-management personnel, including directors, construction managers, quantity surveyors, site agents, and foremen, from SME contractors registered under cidb grades 1 to 6 in the General Building category. Mean rating scores and factor analysis were applied to identify the most significant productivity-enhancing strategies. The findings indicate that SME contractors prioritise effective supervision, regular quality inspections, consistent progress monitoring, timely decision-making, and appropriate task delegation. The adoption of smart technologies such as drone monitoring, telematics for equipment tracking, and blockchain systems for labour payments was also recognised as increasingly valuable. Additional strategies include proper material-handling training, monitoring material usage, efficient waste management, hiring skilled equipment operators, routine machinery maintenance, and maintaining spare machinery parts. Principal component analysis revealed three overarching components for improving labour productivity: site control, smart technologies for productivity enhancement, and site management. This study offers evidence‑based strategies for SME contractors and policymakers, presenting an operational framework designed to minimise project inefficiencies and strengthen sustainable performance in the construction sector.

Impact of infrastructure and housing conditions on health outcomes in Zambia: A scoping review and thematic analysis

Sambo Zulu, Charles Mukumba — Mon, 29 Jun 2026 00:00:00 +0000

Infrastructure and housing conditions are increasingly recognised as key determinants of public health, yet evidence from Zambia remains limited and fragmented. This scoping review maps research on how WASH infrastructure, service provision, and housing quality influence health outcomes. Following the Arksey and O’Malley framework, strengthened by Joanna Briggs Institute (JBI) guidance and reported in line with the PRISMA-ScR checklist, searches across Scopus, Web of Science, PubMed, Google Scholar, and organisational sources identified studies published between 2012 and October 2025. From 4,525 records and 141 full texts, 32 studies met inclusion criteria and were synthesised thematically. Four themes emerged: water and sanitation services, where inadequate or poorly maintained systems drive contamination and disease; WASH access, highlighting persistent inequalities linked to socio-economic status, settlement type, and rapid urbanisation; WASH and health outcomes, showing consistent associations between poor sanitation, limited drainage, water scarcity, and communicable diseases such as cholera and diarrhoea; and housing and malaria, demonstrating how structural features like wall and roof materials, ventilation, and openings affect vector exposure. Across studies, weak sanitation, inadequate drainage, overcrowding, and poor housing quality heightened vulnerability to cholera, diarrhoeal diseases, respiratory conditions, and malaria. Evidence gaps include measuring housing quality, integrating infrastructure factors into health research, and representing peri-urban areas. Findings underscore the need for improved, context-appropriate WASH systems, housing interventions, and standardised assessment approaches, while embedding public health considerations into housing and urban development policies to reduce preventable disease burdens in Zambia.

Why South Africa’s infrastructure maintenance framework has limited practical effect: Policy, practice, and comparative lessons from peer countries

Kevin Wall — Mon, 29 Jun 2026 00:00:00 +0000

Despite the National Infrastructure Maintenance Strategy (NIMS), the Government Immovable Asset Management Act (GIAMA), and the National Immovable Asset Maintenance Management (NIAMM) framework, the condition of South African public sector infrastructure remains unsatisfactory, as evidenced by national ‘report cards’ and the three ‘Drop’ reports that appeared in March 2026. The problem is that there has not (until this article) been a study in South Africa that contrasts the high-level NIMS and its associated NIAMM, on the one hand, with the condition of public sector fixed infrastructure, on the other – and has asked why this strategy and this framework have had hardly any practical effect. This article adopts a qualitative, policy- and practice-oriented approach, drawing on documentary evidence, comparative policy review, and practitioner-informed insight. It investigates the adequacy of implementation of South Africa’s infrastructure asset management guidance, and explores whether peer countries achieve better outcomes through alternative mechanisms. Data were collected through a desktop review of relevant overseas strategies, legislation, and guidelines, supplemented by correspondence with practitioners and professional networks in Australia, Canada, New Zealand, and (to a lesser extent) a few other countries, where documents in English could be obtained. Analysis focused on identifying the presence and effectiveness of governance mechanisms, supportive institutions, and enabling cultures that influence infrastructure maintenance outcomes. Findings indicate that, while South Africa possesses documentation or legislation broadly comparable to that of peer countries, the main reason for these countries’ better infrastructure condition is their prioritising accountability, competence, adequate budgets, and supportive organisational cultures. By contrast, South African strategy and frameworks, largely unsupported and unpublicised, have limited impact. The article highlights implications for strengthening infrastructure asset management policy and practice in South Africa. It does not set out an explicit reform blueprint.