We had perfect weather for carrying out our field test of lime mortars this week. Our research project will advance our understanding of lime mortars and heir durability in extreme conditions. The project is being supported by Historic Environment Scotland.
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St Ninian’s Church is a delightful chapel in Glenurquhart and the congregation have been very supportive of our efforts to conserve this important piece of Highland heritage. The chapel was the first project that Alexander Ross completed and marked the start of his journey to become one of the most renowned and influential architects in the north of Scotland.
The climate in Glenurquhart present a challenge for conservation work, with winter rainfall and temperatures that regularly plunge to below -15 degrees C. This puts enormous stress on lime mortars. The moisture resistance of lime can be improved by the addition of linseed oil, although this can alter other properties of the mortar, reducing the strength. The amount of linseed oil that is used can also have a major influence on performance, a small amount can be beneficial a larger amount can be counter-productive.
Laboratory research has established the principles, our field test will examine if we can take these lessons out of the lab and onto a building site, with all of the practical challenges that can entail.
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The field test involved 3 different mixes of lime and linseed oil, and we will be monitoring how each performs closely over the next couple of years.
Our CPD event on Tuesday was an opportunity to meet the team, Calum Maclean form MAAC Studio and Andrew Beattie from AB Masonry. Our practical demonstration involved the preparation of the different lime mixes and an opportunity to try applying them on the test wall. A hands on opportunity to feel the difference in workability.
Aftercare is important, lime mortar requires carbon dioxide in order to carbonate, this is present in air but must be delivered through the mortar by water. Too much water is a problem, so you need to keep it moist but don't let it get soaked, you also need to prevent it from drying out, hot weather and wind can be equally destructive. The weather this week has been perfect, with mild temperatures between 15 and 18 degrees C, with some broken sunshine, the occasional soft light shower and only very light breezes.
The lime work has been cover for a week and we will shortly by installing the sensors and data loggers.
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MAAC studio are accredited conservation architects and principal designers working with traditional buildings throughout Scotland.
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