Influence of Project Characteristics on Construction Worker Performance: Evidence from High-rise Projects in Nairobi, Kenya

International audience The performance of construction workers is a critical determinant of project success, influencing both productivity and quality outcomes. This study investigates how project characteristics, specifically project value and project duration, affect the performance of construction workers in high-rise building projects in Nairobi, Kenya. A quantitative research strategy and a survey research design were adopted, targeting accredited site supervisors overseeing projects valued above KShs 100 million. Using Cochran’s formula and Bartlett’s correction, a sample of 125 projects was selected, yielding 113 valid responses (90.4% response rate). Worker performance was operationalized through two dimensions: labour productivity (efficiency in task delivery) and labour effectiveness (quality of output and skillset). Data were analyzed using descriptive statistics, ANOVA, and Pearson’s correlation. Results revealed that project value significantly influences both productivity and effectiveness, with stronger effects observed on quality-related outcomes. Project duration also showed significant effects, though correlation analysis indicated a negative relationship with productivity and a weak, non-significant link with effectiveness. These findings suggest that larger and longer projects offer better conditions for training, supervision, and mechanization, enhancing worker effectiveness. However, prolonged durations may erode productivity due to fatigue and resource dilution. The study contributes empirical evidence to Kenya’s construction literature and aligns with regional findings from Nigeria and South Africa. Policy implications include the need for mechanization incentives, regulatory standards, and structured training programs. Practically, contractors should embed supervision and mechanization into project planning, while balancing labour and technology to sustain performance across varying project scales.