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Harling is a rough-cast wall finish consisting of lime and aggregate, known for its rough texture. Many castles and other buildings in
The technique of harling features in a large number of famous Scottish buildings including:
*
Scottish Lime Centre
Building Architecture in Scotland Plastering Building materials
Harling is a rough-cast wall finish consisting of lime and aggregate, known for its rough texture. Many castles and other buildings in Scotland
Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...
and Ulster
Ulster (; ga, Ulaidh or ''Cúige Uladh'' ; sco, label= Ulster Scots, Ulstèr or ''Ulster'') is one of the four traditional Irish provinces. It is made up of nine counties: six of these constitute Northern Ireland (a part of the United King ...
have walls finished with harling. It is also used on contemporary buildings, where it protects against the wet Scottish and Ulster climates and eliminates the need for paint.
Technique
Harling as a process covers stonework using aplaster
Plaster is a building material used for the protective or decorative coating of walls and ceilings and for Molding (decorative), moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of ...
ing process involving a slurry of small pebbles or fine chips of stone. After a wall is complete and has been pointed and allowed to cure then a base of lime render
Lime render is the first coat of lime "plaster or the like" applied to the external surfaces of traditionally-built stone or brick buildings.
It allows the building to 'breathe' – as lime is porous, it allows for the collection and evaporation ...
is applied to the bare stone. While this render is still wet a specially shaped trowel is used to throw the pebbles onto the lime surface, which are then lightly pressed into it. Harl, being mostly lime render, cures chemically rather than simply drying. After this setting process, the harl is sometimes lime washed in a colour using traditional techniques.
It is not recommendable to replace more than around 20% of the lime content with cement
A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate) together. Cement mix ...
. Cement-based render is very stiff and prone to crack or detach from the wall when subjected to stress induced by expansion due to solar radiation and moisture. It is also less permeable to moisture and water vapour. Water entering through fine cracks in the surface does not easily diffuse and can penetrate into the softer stone, thus causing the deterioration which harling aims to prevent. For similar reasons, modern barrier paints should not be used in place of traditional lime washes.
An example of the inadequate protection afforded by high cement harling is the Charles Rennie Mackintosh
Charles Rennie Mackintosh (7 June 1868 – 10 December 1928) was a Scottish architect, designer, water colourist and artist. His artistic approach had much in common with European Symbolism. His work, alongside that of his wife Margaret Macdo ...
designed Hill House completed in 1904 using the newly available but poorly understood Portland cement
Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th c ...
harling. Over the years water had penetrated the harling and threatened the overall integrity of the building. The National Trust for Scotland
The National Trust for Scotland for Places of Historic Interest or Natural Beauty, commonly known as the National Trust for Scotland ( gd, Urras Nàiseanta na h-Alba), is a Scottish conservation organisation. It is the largest membership organ ...
, the building's owner, has (2019) enclosed Hill House in a transparent 'box' which will allow some rain to enter but which will eventually allow it to dry naturally. It is estimated that this will take seven to ten years, after which the box will be removed.
Examples
The technique of harling features in a large number of famous Scottish buildings including:
* Clark Cottage
Clark Cottage is a residential building in the Scottish village of Port Charlotte on the island of Islay. The building is on the eastern side of ''Main Street'' in the south-eastern part of the town. On 28 August 1980, Clark Cottage was liste ...
on the island of Islay
Islay ( ; gd, Ìle, sco, Ila) is the southernmost island of the Inner Hebrides of Scotland. Known as "The Queen of the Hebrides", it lies in Argyll just south west of Jura, Scotland, Jura and around north of the Northern Irish coast. The isl ...
* Crathes Castle
Crathes Castle (pronounced ) is a 16th-century castle near Banchory in the Aberdeenshire region of Scotland. It is in the historic county of Kincardineshire. This harled castle was built by the Burnetts of Leys and was held in that family for ...
in Aberdeenshire
Aberdeenshire ( sco, Aiberdeenshire; gd, Siorrachd Obar Dheathain) is one of the 32 Subdivisions of Scotland#council areas of Scotland, council areas of Scotland.
It takes its name from the County of Aberdeen which has substantially differe ...
(16th century)
* Craigievar Castle
Craigievar Castle is a pinkish harled castle or fortified country house south of Alford, Aberdeenshire, Scotland. It was the seat of Clan Sempill and the Forbes family resided here for 350 years until 1963, when the property was given to the ...
in Aberdeenshire (17th century)
* Muchalls Castle
Muchalls Castle stands overlooking the North Sea in the countryside of Kincardine and Mearns, Aberdeenshire, Scotland. The lower course is a well-preserved Romanesque, double-groined 13th-century tower house structure, built by the Frasers of ...
in Aberdeenshire
* Myres Castle in Fife
Fife (, ; gd, Fìobha, ; sco, Fife) is a council area, historic county, registration county and lieutenancy area of Scotland. It is situated between the Firth of Tay and the Firth of Forth, with inland boundaries with Perth and Kinross (i ...
(1530 onwards)
* Stirling Castle
Stirling Castle, located in Stirling, is one of the largest and most important castles in Scotland, both historically and architecturally. The castle sits atop Castle Hill, an intrusive crag, which forms part of the Stirling Sill geological ...
in Stirling
Stirling (; sco, Stirlin; gd, Sruighlea ) is a city in central Scotland, northeast of Glasgow and north-west of Edinburgh. The market town, surrounded by rich farmland, grew up connecting the royal citadel, the medieval old town with its me ...
See also
*Stucco
Stucco or render is a construction material made of aggregates, a binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as a decorative coating for walls and ceilings, exterior walls, and as a sculptural and a ...
* Roughcast
Roughcast or pebbledash is a coarse plaster surface used on outside walls that consists of lime and sometimes cement mixed with sand, small gravel and often pebbles or shells. The materials are mixed into a slurry and are then thrown at the wor ...
* Pargetting
Pargeting (or sometimes pargetting) is a decorative or waterproofing plastering applied to building walls. The term, if not the practice, is particularly associated with the English counties of Suffolk and Essex. In the neighbouring county of Nor ...
References
{{reflistExternal links
Scottish Lime Centre
Building Architecture in Scotland Plastering Building materials