Laser scanning technology is a fast and reliable method to survey structures. However, the automatic conversion of such data into solid models for computation remains a major challenge, especially where curved and complex features are presented. Since openings and the overall dimensions of the buildings are the most critical elements in 3D models, the Slicing Method introduces as a new, computationally-efficient method for extracting overall façade and window boundary points for reconstructing a façade into a geometry compatible with computational modelling. After finding a principal plane, the technique slices a façade into limited portions, with each slice representing a unique, imaginary section passing through a building. This is done along a façade’s principal axes to segregate window and door openings from structural portions of the load-bearing masonry walls. The method detects each opening area’s boundaries, as well as the overall boundary of the façade, in part, by using a one-dimensional projection to accelerate processing. Accuracy in excess of 93% was achieved with no manual intervention on highly complex buildings and nearly 100% on simple ones. Furthermore, computational times were less than 3 sec for data sets up to 5.2 million points, while similar existing approaches required more than 16 hr for such datasets.