On the Use of Iron Elements in Southern Bavarian Roofs of the Baroque

We report on structural iron elements employed in southern German timber roof constructions erected between 1600 and 1800. We discuss the diversity of forms of iron members employed, ranging from fasteners with keys and nuts, to straps, as well as iron anchors and rods. Iron was originally used mainly for joints subject to tensile stress; we demonstrate how, initially, iron connectors were introduced as subsidiary fasteners in addition to traditional carpentry joints, and show how they finally tended to replace the traditional carpentry joint altogether. This can be studied by the example of the king posts. Iron also became almost indispensable in the construction of the typical Bavarian baroque roofs which usually lack tiebeams, in favour of high vaults; the thrust of these roofs is usually carried by highly stressed scissor braces. The joints associated with scissor braces are another issue where iron replaced traditional jointing. We also show some exceptional uses of iron in the form of larger straps, rods and anchors, which helped to solve exotic design challenges where very high stresses had to be transmitted or "tightening" of the connection would be desirable.