Good building layouts are required to conform to regulatory guidelines,

while meeting certain quality measures. While different methods

can sample the space of such good layouts, there exists little

support for a user to understand and systematically explore the samples.

Starting from a discrete set of good layouts, we analytically

characterize the local shape space of good layouts around each initial

layout, compactly encode these spaces, and link them to support

transitions across the different local spaces. We represent such

transitions in the form of a portal graph. The user can then use the

portal graph, along with the family of local shape spaces, to globally

and locally explore the space of good building layouts. We use

our framework on a variety of different test scenarios to showcase

an intuitive design, navigation, and exploration interface.