Carpentry craft at the turn of the 18th and 19th centuries. Case study: the roof structure of the Church of the Holy Cross in Leszno

Ulrich Schaaf, Maciej Prarat

doi:10.37190/arc220104

Abstract

In 1790, a fire consumed the upper part of the Church of the Holy Cross in Leszno, which was built in the years 1711–1715. The reconstruction of the roof structure and the vaults took place in 1798–1802. It was an extremely complicated task because it was a construction spread over a rectangular body measuring 24 × 44 m with an elongated, vaulted octagon inscribed in the body. The purpose of this text is to present this complex construction. The research method consisted in the analysis of the structural system and layout, carpentry joints, building materials, their processing, and the system of carpentry assembly marks. The architectural research carried out in conjunction with the study of sources and literature on the subject enabled the reconstruction of the building history from the end of the 18th century to the 2nd half of the 20th century, and the recovery of the originally used carpentry craft. The discussed structure is a free collar beam roof structure with a hanging king post structure lying on the lower tier and a king post truss structure on the upper one. The king post was additionally supported by passing braces and braces reaching through both tiers, and the straining beam was also strengthened by additional passing braces on the lower tier. These solutions are known from the hanging and strutted frame and strut frame structures. Moreover, short tie beams were suspended from the king post or queen post structure within the inner octagon. This complex structural system required the use of various types of roof trusses, from the principal rafter truss and paired common rafter to the corner and jack-tie rafter. They also come in different varieties and variants. The results of the research may become a contribution to a broader analysis of the carpentry craft at the turn of the 18th and 19th centuries.

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