We describe a new algorithm for floorplan evaluation using timing-driven buffered routing according to a prescribed buffer site map. Specifically, we describe a provably good multi-commodity flow based algorithm that finds a global routing minimizing routing area (wirelength and number of buffers) subject to given constraints on buffer/wire congestion and sink delays. This permits detailed floorplan evaluation, i.e., computing the tradeoff curve between routing area and wire/buffer congestion under any combination of delay and capacity constraints.Our algorithm (1) enforces maximum source/buffer wireloads; (2) enforces wire and buffer congestion constraints by taking into account routing channel capacities and buffer site locations; (3) enforces individual sink delay constraints; (4) performs buffer/wire sizing and layer assignment; and (5) integrates pin assignment with virtually no increase in runtime. Preliminary experiments show that near-optimal results are obtained with a practical runtime.