The design and construction techniques of eighteenth century timber roofs in Scotland: Glasgow trades hall and tweeddale house in Edinburgh

The few open roofs mentioned in literature seem to represent an exception rather than the rule: most Scottish timber roofs are hidden behind timber or plaster ceilings and characterised by a much simpler common rafter form. From the eighteenth century onwards they presented hipped and trussed arrangements as well as other more complex solutions developed to meet the requirements of evolving architecture. This paper attempts to shed some light on the design and construction techniques of eighteenth century Scottish timber roofs with the preliminary results obtained from the creation of a relational database of 1250 buildings (including structures, professionals, dates), related mapping, survey of 29 roofs across Scotland and a more detailed study of those at Tweeddale House in Edinburgh, and Glasgow Trades Hall. Both buildings have roofs from the period in which the Adam brothers worked on them as architects. The original sixteenth century Tweeddale House was remodeled by the Adams in 1752-3 and almost forty years later Robert Adam designed the Glasgow Trades Hall (1791/4), although the building was completed after his death with a modified design. Archival research combined with surveys has allowed to make an initial appraisal of the design and construction processes involved in the two projects. Many questions arise concerning the specific involvement of architects and wrights in the successive transformations of the roofs and an attempt to identify local and foreign influences has been carried out by analyzing the typology of roofs and joints.