Modeling and numerical analysis of the design of building structures, their technology, organization and management methods of construction processes are the subject of the work of many scientists in Poland. Schedule designers try to best reflect the reality of construction projects with the available methods, although this procedure is not always successful. One of the scheduling methods is the Time Coupling Methods (TCM), which can be refined using the predictive durations of the Multivariate Method of Statistical Models (MMSM) construction processes and standard deviations. A new scheduling method in the probabilistic approach was developed – Probabilistic Time Couplings Method I (PTCM I). At PTCM I, work is organized in such a way as to maintain the continuity of work of employees, as downtime of workers is disadvantageous and costly. The total duration of the new investment was forecasted and compared with the other methods of scheduling and with real time after its completion. The results clearly show that the developed methodology can be successfully used in scheduling construction works.