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Greyfriars Townscape Heritage Initiative

Introduction to lime plastering

Blog written by Francesca Bufano and David Gladstone.

The Greyfriars Townscape Heritage Initiative is a five year heritage led regeneration programme. Their stated aim is to ensure the long-term sustainability of the area by preserving, restoring and enhancing its cultural heritage. As part of their initiative to reinvigorate the Greyfriars area, the programme has aimed to provide training to local community organisations, businesses and property owners to encourage a greater understanding of their historical environment.

To build upon our understanding of heritage and restoration within the local community three members of our team attended a one day course that allowed us to gain an understanding of why lime has been used in historic buildings, the different applications of lime and why its continued use and application is important for maintaining both the character and the structural integrity of historical buildings. The course included the practical elements of working with lime including the finishing and aftercare required. This was lead by Philip A Gaches, a master of plaster and decorative arts, who has worked on historic buildings in Britain and internationally since 1948.

Philip introduced us the history of lime plaster and how it has developed with technology and fashion while focusing on the style and methods used within buildings after the 1700s. We briefly covered the manufacturing process of lime and the chemical processes involved. This helps with understanding the different components within the material and the subsequent types of lime plaster and their application. The material itself is extremely durable within the correct environment and application.

Historically, buildings have been designed in a way that allows for the movement of moisture through the structure. In the case of a masonry wall, the moisture from within the building will move through the porous materials chosen within the construction. This system has been disrupted in the past through the use of non-porous materials within restoration work. An example of this is the use of cement when re-pointing a masonry wall. This lack of knowledge of historic building techniques causes irreparable damage to the wall as moisture build up weakens and breaks down the masonry.

How is this relevant to our work?

Having a greater understanding of the process of lime plastering allows us to have informed conversations with contractors to agree on the best type of lime plaster and how it will be applied as well as making us more qualified to oversee the work being done by the contractor. Another important aspect that we were taught was how we can do an on-site assessment of lime mortar to determine its composition. This can be done by hand crushing a piece of the existing lime mortar and examining the aggregates and hair that have been added to the lime putty.

Another topic that Philip covered in his workshop was the different construction methods of a wall or ceiling that can have lime plaster applied to it. This can either be masonry or lathes (thin timber strips between joists) and he outlined the advantages of riven (hand split) oak lathes over sawn oak or pine lathes and the cost implications. He also illustrated how reeds could be used in conjunction with lathes in order to provide an alternative base for the lime plaster that was cheaper but still of a high quality.

After the interactive element of the workshop, we learned that almost all of the issues that can occur when using lime plaster are caused by moisture build up, either directly or indirectly by attracting beetles that can damage the wall structure, such as woodworms.

To conclude, the workshop was very informative with regards to the processes and history of lime plastering but also very interactive and engaging with the practical element. It is important for us to learn about different trades associated with construction, especially regarding conservation of a heritage building as it allows us to best inform the client as well as ensuring that any works done are appropriate to the context and period of the building. We would recommend others to participate in other upcoming Greyfriars Townscape Heritage Initiative workshops.

For more information on the Greyfriars Townscape Heritage Initiative please visit their website linked below.