Buildability is one of the most important factors affecting construction labour productivity. Nonetheless, an extensive search of the literature revealed a dearth of research into its effects on in situ reinforced concrete construction, especially at the rebar fixing trade level. Buildability factors affecting rebar fixing labour productivity of major structural elements, such as foundations, columns, walls, beams and slabs, are yet to be investigated and quantified. In comparison with the other constituents of the reinforced concrete frame, rebar fixing in beams is one of the most labour-intensive and time-consuming activities, therefore, the objective of this research is to quantify the effects and relative influence of buildability factors on fixing labour productivity of beams. To achieve this objective, a large volume of productivity data was collected and analysed using the categorical interaction-regression method. As a result, the effects of the variability of beam sizes, rebar diameter, stirrups diameter, reinforcement quantity, beam dimensions, and span geometry are determined. The findings show a significant influence of these factors on the labour efficiency of the fixing operation, which may be used to provide designers and construction managers with feedback on how well the designs of this activity consider the requirements of buildability, and the consequences of designers' decisions on the labour productivity of the operation. In addition, a set of recommendations are presented, which upon implementation, can improve the buildability level of this activity, thus translate into higher labour productivity and more efficient utilization of resources.
