Repairing a Medieval Door

Abstract

The main doors of medieval buildings or building complexes such as cathedrals or palaces are substantial structures, often weighing as much as one tonne per leaf. A survey of medieval English doors shows several distinct structural types whose different structural actions will be considered. All must develop some form of in plane action through the interaction of their components to transmit their weight back to their supports. However their complexity often allows several different modes of action, each of which will be differently affected by moisture movement within the timber, so that more than one mode of action will often need to be considered. The recent need to repair the early sixteenth century main doors of Trinity College, Cambridge involved the detailed analysis of one of these types whose structure comprised a dense grid of relatively slender muntins and ledges set within a much more substantial frame, carrying decorated boarding and mouldings on the outside face. The intention was that by understanding this structure we would be able to restore the original structural action of the door. In this case earlier interventions and permissions, and the extent of deterioration at the lower hinges, made this impossible. However, the exercise suggests an approach that might be valuable in the restoration of other doors of this type.