With increasing regularity, compartments with exposed timber boundaries are being proposed in high-rise buildings. However, due to the combustible nature of timber, the fire-specific risks associated with these decisions must be thoroughly explored. In particular the requirement that the timber stops burning after the imposed fuel load has been consumed must be fulfilled. By means of reduced scale experiments it was determined that sustained burning was dependent on both the configuration of exposed faces and, to a lesser extent, the imposed fuel load. The principal factor for auto-extinction or otherwise was found to be in the configuration of exposed surfaces, with two exposed walls (in this case back and side wall) consistently resulting in sustained burning. When a wall and the ceiling were left exposed (wall opposite the compartment opening and ceiling), auto-extinction occurred for all but the highest fuel load considered. The occurrence of char fall-off (delamination) was significant in promoting sustained burning and was observed to cause a transition from apparent extinction back to flaming in one experiment.