'G' is for green serpentine stone, eroding on some older Lancaster facades [architecture column]

ARCHITECTS’ ALPHABET, PART 7:

“G” IS FOR GREEN SERPENTINE STONE

The Architects’ Alphabet is a 26-part series describing design elements featured in Gregory J. Scott’s upcoming book, “Urban Legend, The Life & Legacy of C. Emlen Urban,” Lancaster’s most renowned architect. Photos for the book, which is to available for pre-sale at egganddartbooks.com., are by Matthew Tennison.

Between 1880 and 1900, a new masonry product from Chester County arrived on the scene in Lancaster. Green serpentine stone captured the attention of builders and homeowners alike. The uniquely different “sage green” cut-stone facades began to appear along the two most desirable street addresses in the city: West Chestnut Street and North Duke Street.

Green serpentine stone from Chester County captured the attention of builders and homeowners in Lancaster County between 1880 and 1900. It turned out the stone was prone to erosion and crumbling. Here are some examples of the stone in use on local houses.

All the most prominent and influential contractors and architects of the time added the green serpentine structures to their portfolios, except C. Emlen Urban.

Urban spent a great deal of time researching the materials he would specify for his buildings. His June 13, 1889. handwritten journal denotes the results of an experiment he performed relating to the water absorption rate of certain masonry products, including bricks.

Urban weighed each unit before and after several hours of submersion. With this information in hand, he knew which products would “wick” rain and moisture at a higher rate and could, therefore, predict their performance. Perhaps he was suspicious of the “new” product that was growing in popularity in the most prestigious neighborhoods.

Andrew Baker mansion, built in 1891 on Main Street, Ephrata, for hotel owner Andrew Baker, features green serpentine stone.

Green serpentine stone is found in only four states: Pennsylvania, Maryland, Oregon and California. A quarry in Chester County provided Lancaster’s supply of the material. The homes with green serpentine are easy to identify; their facades are crumbling and “shedding their skin” before our eyes.

The reason for this rapid deterioration is quite simple: Serpentine is a soft stone composed of hydrous magnesium silicate, the same material found in talcum. Because of its fibrous nature, it absorbs water resulting in expansion and contraction, and eventual deterioration. Its popularity was short lived, but not before it found its way to New York, Baltimore, Philadelphia and even Chicago.

These green serpentine stone facades on homes from the 1880s on West Chestnut Street, once known as Holman Row, have been preserved and painted. They were designed by architect Frederick P. Dinkelberg.

Many Lancastrians have painted their green stone to slow the erosion while others have applied a silicone water-repellent coating. Unfortunately, the only remedy after severe decay is to remove the stone and replace it with another more suitable masonry product. Interestingly, Urban’s own father used the material on houses he and his partner constructed on West Orange Street in 1880.

Did C. Emlen foresee the potential problem with the green serpentine and avoid specifying it on his own commissions? We may never know the answer.

Beyond the unusual green color, what is the name of the surface texture on the stones?

The texture is referred to as “frosted” or “hammered.”

Is the deterioration of the green stone a structural concern?

Typically, the stone is anchored to structural brick or block. The green stone is non-structural.

Did C. Emlen design homes for his father’s business?

In 1873, Amos Urban and Henry Burger formed Urban and Burger Planing Mill and built homes in the city. C. Emlen may have had a hand in designs from 1879 until his father’s passing in 1888.

This column is contributed by Gregory J. Scott, FAIA, a local architect with 50 years of national experience in innovation and design. He is a member of the American Institute of Architects’ College of Fellows. Email [email protected].

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