Successful implementation of the Critical Path Method requires availability of clearly defined duration for each activity, while the PERT method is based on personal estimation. However, due to the long duration of the construction and unpredicted delays that accompany this process, it is often difficult or almost impossible to predict exact duration of an activity, and consequently to take it for granted that the given activity will be finished on the very same day that is given in the dynamic plan of construction.The aim of presented research was to establish methodology for developing new productivity norms for construction works for planing under uncertainty.