Historic External Lime Finishes In Scotland

Citation

Meek T & Addyman T (2019) Historic External Lime Finishes In Scotland [Technical Paper 31: Historic External Lime Finishes In Scotland]. Historic Environment Scotland. Historic Environment Scotland Technical Papers, 31. www.historicenvironment.scot/TechnicalPapers. https://www.historicenvironment.scot/archives-and-research/publications/publication/?publicationId=9fc7b2b3-e3a1-4b4c-8b5b-aa8b00908af2

Abstract
The external finish of a building is the first line of defence in protecting the masonry from the elements. Traditional solid masonry wall construction relies on a combination of robust building materials and techniques: outer skins of lime bonded masonry with a lime or earth/lime core and, historically, an external lime coating. This lime coating, whether flush lime pointing, harling or more formal pressed back and lined out render with limewash served a dual purpose: it protected the masonry from the driving rain, wind scouring and frost, and it presented a uniform finish, concealing rubble masonry and giving a bright, even finish to the elevations. This outer layer of limewash is by its nature sacrificial, and regular reapplication is required to maintain the finish, especially in exposed locations. Left unattended, limewash and the lime harling and pointing underneath will gradually be worn away, exposing the stone, at first gradually and eventually almost completely, giving an appearance of flush pointing or bare masonry. The practice of removing harling or raking out and re-pointing previously harled buildings, has further established the modern aesthetic for exposed rubble stone buildings. This trend has resulted in a visually altered and arguably inauthentic presentation of the historic environment, very different to how it would have appeared in the past, and buildings that are technically less resilient against the weather. This Technical Paper sets out the historical background to external lime coatings on traditional buildings, and provides a series of illustrated examples where the historic finish remains, either substantially or in part. The careful observation of buildings, seeking out sheltered areas such as under eaves, in window reveals or in the corners or return wall where buildings meet, will show up vestiges of these finishes almost universally across Scotland. Raising awareness of the surviving traditional finishes, their composition, appearance and function, will help improve our understanding of how traditional buildings should be repaired, conserved and sometimes adapted to improve resilience to a changing climate.

Keywords
Harl, Lime Mortar, limewash, Conservation, Stone Decay, Water Penetration, Climate Change