Abstract The reciprocal effects of tunnelling-induced ground settlement and surface buildings are among the main concerns in urban underground projects. Interactions between buildings and tunnels can have major effects on the settlement trough. Therefore the factors involved in this interaction need to be assessed prior to construction. The interaction of twin tunnels construction and buildings has been less studied compared to single tunnels. In this paper, the authors present the results of a study on field data of the Shiraz metro line1 and conduct two dimensional numerical parametric simulations. The effects of different factors such as tunnels’ depth and their center to center distance, and buildings stiffness, their weight, width and locations on the surface are assessed. Based on the results of the numerical simulations, the influence of each factor on the settlement trough is assessed and a new parameter named ‘relative bending stiffness’ is introduced to incorporate these factors. Two design graphs are developed for fast evaluation of the buildings effects on surface settlements in preliminary design phases. These graphs relate the maximum building settlement caused by tunnelling to the corresponding green-field settlement.