Specifying Historic Materials: The Use of Lime

Abstract

Despite technological advances of the 21st century, mortars and stuccos for masonry restoration projects continue to be specified using portland cement. Without standards or codes specifically designed for historic buildings, owners and contractors often unknowingly incorporate incompatible materials into historic repairs. Using recent restoration projects in the United States and Hungary as case studies, this paper focuses on the need for mortar and stucco standards specifically oriented towards the specification of mortars and stuccos for historical structures, the practical reasoning behind this need, and the historical documentation that supports this premise. In particular, the critical importance and potential applications of lime are addressed. Past and present repairs using cement and lime, why they differ, and the effect they have had will be addressed. The structures these studies focus on predate portland cement's existence and are historical precedents for the use of lime mortars and stuccos. Finally, current ASTM specification efforts related to lime mortars are reviewed, and further development in this area is encouraged.