In recent years, SPNEA's preservation staff has come to share the belief widely held in the United Kingdom that old stone structures were commonly protected by lime-based mortars and parges, which enabled the masonry to shed water. Working with the preservation group Historic Scotland, SPNEA imported a Scottish preservation mason to teach its crews the ancient principles and techniques of working with lime. The side wall at the c. 1687 Arnold House in Lincoln, Rhode Island, a characteristic local building type known as a "stone ender," has just been repaired using these "new," but actually old, methods. Previous repairs to the Arnold House carried out in the mid twentieth century had neglected to install the lime outer layers that worked to protect the masonry, which resulted in water infiltration that damaged both the wall and the interior.
Relying on photographic research and on-site evidence, SPNEA embarked on a three-year program to restore the lime system that most likely had originally been used on the building's stone end. The crew's first step was to rake the joints to remove loose mortar. They then "cherry cocked" the masonry mass with "gallets," by inserting stone chips and pebbles into the masonry wall to support the larger stones. Next, they "sneck harled" the entire surface by applying lime mortar to make the joints flush with the stone face. The final step was to "harl" the surface with several coats of lime wash to seal it.
The harled finish at the Arnold House, in addition to protecting the building for years to come, dramatically alters its appearance. A smooth bright finish now conceals the field stone surface that once seemed to epitomize the rugged existence of New England's first settlers.
Director of Building Preservation