Purpose: In this study, the authors develop a method for the estimation of uncertainties arising from the building material service-life in the context of building LCA and LCC. Method: Life Cycle Assessment and Life Cycle Costing analysis were conducted on four newly built Swiss dwellings. The related uncertainties arising for the variability of the building material service lives was evaluated with a Monte Carlo simulation. Findings: The outcome of the study shows that the greenhouse gas emissions or the cost uncertainties of the replacements represent between 6 and 16% of the total result of the buildings’ LCA or LCC. Furthermore, the uncertainties’ estimation of the replacements allows to compare more accurately the buildings’ environmental or economic performances. Conclusion: The study highlights the interest of taking into account uncertainty estimation for the replacement phase, especially in the context of more energy efficient buildings.