This study describes the impact of the use of mechanised equipment on physical load and workers' health among road workers and floor layers by comparing the traditional manual work method with frequently occurring scenarios of use of this new equipment. Continuous direct measurements of postures were linked to real-time observations of tasks and external forces applied during manual materials handling. A self-administered questionnaire on musculoskeletal complaints was used. The introduction of a hydraulic clamp or vacuum lift to assist roadmakers while laying a brick-paved road reduced the team's work time in a kneeling/squatting position with 43-52% and frequency of lifting loads of 5-15 kg and above 15 kg with 46-59% and 84-88%, respectively. The introduction of a mixing machine with a pump system during pouring of sand-cement floors reduced the frequency of lifting loads with 66% for 5-15 kg and 15% for over 15 kg, but had no discernable effect on awkward back postures. The use of a silo/truck with automated pump system also reduced the frequency of lifting with 32% and 38%, respectively, but increased the duration in awkward back postures with 13%, primarily due to the hodman partly working as floor layer. Floor layers and hodmen using the mechanical equipment reported a lower prevalence of low back pain in the past 6 months and also less associated sick leave. The introduction of new mechanised equipment resulted in changes in physical load per task within jobs, changes in task distribution within jobs, and changes in work organisation and jobs within a team. The judgement of experts on the impact of new devices on physical load should be corroborated in field studies on the average exposure to physical load per work day and per team. Relevance to industry: The study demonstrated the preference of a scenario approach in evaluating the impact of interventions on physical load above the classical analysis of the most strenuous task.