Jam doughnut

Abstract: An ‘architectural doughnut’ is a building with a plan consisting of two concentric circles. Two types are distinguished: the ‘ring doughnut’ where the central circle is a courtyard, and the ‘jam doughnut’ where some important central space (the ‘jam’) is surrounded by a ring of smaller spaces (the ‘dough’). The main emphasis is on the second type. A series of historical examples is discussed including locomotive roundhouses, Panopticon prisons, hospital wards, parking garages and offices. The ratio of the diameters of the circles is shown to be important for the functioning and even the feasibility of ‘jam doughnut’ plans, depending on the activity housed. In several of the case studies the doughnut shape results in serious inefficiencies in the use of space. Such plan types were soon abandoned. Geometrical data on all the examples are presented in a ‘morphospace’ or world of possible doughnut plans.