In construction projects, losses of productivity often incur additional costs and construction time delays, giving rise to disputes and legal proceedings, and the commissioning of expert opinions. In practice, it is usually assumed that labor consumption rates remain constant even if influential parameters change, which means a linear output curve. Only a few approaches to determining and calculating losses of productivity are presented in the literature, largely considering influences only on a certain subset of productivity. However, various disruptions may occur at the same time during the construction period, which is why the individual losses of productivity affect each other, thus aggravating their effects. This paper demonstrates how various losses of productivity – in relation to reinforced-concrete works – can be aggregated. Furthermore, this model subsequently enables both deterministic and probabilistic evaluations whilst considering the non-linear correlations between changes in the influential parameters and the resulting losses of productivity. In the probabilistic approach, the potential risk and/or chance can be captured using distribution functions. Decisions can thus be made on the basis of a defined certainty level. This approach aims to optimize the utilization of productivity factors and determine costs according to their sources, if available resources cannot be used optimally and productivity losses appear likely.