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What the heck is sneck harling?

September 29, 2015

 Fig 5

How do historic stone structures like the 1690 manor house at Spencer-Peirce-Little Farm in Newbury, Massachusetts, survive centuries of New England weather? Sometimes an extra layer of protection can help.

In the late 1990s and early 2000s, the east end of the manor house was covered with a lime-based protective coating known as harl. Harling is a traditional practice for covering stone structures, widely used in Scotland and other parts of the British Isles. Essentially a type of stucco or parging, harl is a sacrificial weathering layer that is easily renewed.

First, irregularities in the surface of a wall are filled with small stones in a process called galleting. In the next step, known as sneck harling, the surface is covered with a mixture of lime and sand. After these denser layers are applied, the surface is covered with several coats of lime wash or whitewash. The whitewash is easily renewed when it begins to weather, which keeps the stones and mortar protected from deterioration.

The harl on the manor house at Spencer-Peirce-Little Farm has been re-treated twice, once in 2009 and again in spring 2015. These regular maintenance activities are an integral part of traditional building practices. They protect the core of the structure by renewing weather-facing materials before the inner layers are exposed.

Please consider helping Historic New England maintain historic buildings with a gift to the Preservation Maintenance Fund.

See the step-by-step process below:

Fig 1
First, we removed loose whitewash and harl from the wall.

Fig 2
Harl is hand-mixed from lime, water, and sand in small batches that can be applied within about an hour.

fig 3
New harl is applied to the missing areas and troweled until it's as smooth as the surrounding surfaces.

Fig 4
Because harl and whitewash cure by a chemical reaction with water (not by drying), the wall must be kept damp during the entire process. This requires frequent wetting of the surface and a covering to prevent drying.

Fig 5
The result is both weather-ready and visually striking.

sneck harling and galletting

Posted by clemency coggins on October 14, 2015
These are neat. Now use them in sentences 5 times so you don't forget.

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What the heck is sneck harling?