The construction of new foundation pits inevitably disturbs adjacent existing buildings. Rapid and effective assessment of the degree of construction-induced disturbance is therefore a critical engineering challenge for the rational formulation of design and construction schemes. In this study, a case-based multicondition analysis is implemented using a two-stage numerical modeling framework that integrates the finite element method (FEM) and the extended finite element method (XFEM). The reliability of the proposed model is validated through comparison with field-measured data. Subsequently, a response surface-based prediction model is developed. Based on the crack expansion area and parameter sensitivity analysis, impact zoning of construction disturbance on buildings with varying initial damage levels is evaluated in relation to adjacent construction parameters. The results demonstrate the following: (1) The proposed FEM-XFEM two-stage model is effective for analyzing crack propagation in buildings subjected to disturbances induced by newly constructed foundation pits. (2) The crack propagation area shows a strong correlation with disturbance intensity. Under level Ⅱ influence conditions, the crack propagation area mainly ranges from 0.8 to 1.4 m²; therefore, 0.8 m² and 1.4 m² can be adopted as threshold values distinguishing influence levels Ⅰ/Ⅱ and Ⅱ/Ⅲ, respectively. (3) The distance between the foundation pit and the existing building (D) shows a clear correlation with the crack propagation area. Specifically, when D > 21 m, 3.9 m < D≤ 21 m, and D≤ 3.9 m, the corresponding influence levels are Ⅰ, Ⅱ, and Ⅲ, respectively. (4) When initial building damage is considered, foundation pit construction is classified as level Ⅰ influence if the initial crack length is less than 41% of the wall length and the crack width is less than 67% of the wall thickness; whereas it is classified as level Ⅲ influence when the initial crack length exceeds 66% of the wall length or the crack width exceeds 83% of the wall thickness.