Specification and time required for the application of a lime-based render inside historic buildings

Abstract

Intervention in ancient buildings with historical and architectural value requires traditional techniques, such as the use of lime mortars for internal and external wall renders. In order to ensure the desired performance, these rendering mortars must be rigorously specified, and quality controls must be imposed during application. The choice of mortar composition should take account of factors such as compatibility with the substrate, mechanical requirements, and water behavior. The construction schedule, which used to be considered a second-order variable, now plays a decisive role in the selection of the rendering technique, given its effects upon costs. How should lime-based mortars be specified? How much time is required for the application and curing of a lime-based render? This article reflects upon the feasibility of using traditional lime mortars in three-layer renders inside churches and monasteries under adverse hygrothermal conditions and when time is critical. A case study is presented in which internal lime mortar renders were applied in a church in northern Portugal, where the very high relative humidity meant that several months elapsed before the drying process was complete. [Editor's note: The Portuguese title of this article is: "Especificação e tempo de aplicação de um reboco tradicional à base de cal no interior de edifícios históricos."] Author Abstract LB - D5 LB - Building materials, processes of deterioration and treatment