(https://www.solorealty.com/the-secret-life-of-buildings-star-bolts/)
Have you ever noticed stars on the façade of Philadelphia row homes as you walk down any older neighborhood street in Philadelphia? Many people believe these stars are purely decorative, however these stars are essential to keep the building standing. These “stars” are referred to as Star Bolts. Row homes are built by connecting joists between the adjoined walls, often referred to as “party walls.” The front and rear walls of the row homes are only connected at the edges of the adjoined “party walls.”
(http://www.tonerarch.com/blog/2013/6/13/your-house-and-your-facade-a-separation-agreement.html)
Over a period of time, the front and rear exterior walls will begin to separate from the rest of the structure. There are numerous causes for the separation of the exterior walls from the rest of the structure. These reasons vary from foundation issues, to the brick and mortar itself. A mason will determine how many joists will be needed to connect the exterior wall with the floor and ceiling joists. The degree of bulge in the wall will determine how many joists will be need to be connected to the star bolt. The concept of using these style of rods to dates back to Roman Era engineering. Romans were known to use rods of metal or wood to help negate the outward horizontal forces present in many of their large stone structures.
(https://www.solorealty.com/the-secret-life-of-buildings-star-bolts/)
Philadelphia’s is home to over 300,000 thousand row homes. Various styles of row homes were created to fulfill the need to house Philadelphia’s population throughout the cities growth over many generations. Some of these styles of row homes were Bandbox, London House Plan, City House Plan, and the Town House Plan. A significant feature which is found in all theses styles of row homes, is the use of brick and mortar.
(https://www.curbed.com/2017/3/16/14945986/tiny-house-philadelphia-trinity-for-sale)
The majority of Philadelphia’s ground was composed of clay. During early brick production in Philadelphia, the area between the Delaware River, and the Schuylkill was considered the best quality of clay in the area. This natural resource played a vital role in the need to create more homes throughout Philadelphia’s History.
(https://hiddencityphila.org/2012/08/red-brick-said-gold/)
By the end of the 19th century, it was estimated that Philadelphia was producing over 200 million bricks per year over a two century timeframe. However due to a reduced amount of clay resources, and the cheaper, quicker uses of concrete, Philadelphia brick production almost ceased to exist.
(https://www.solorealty.com/the-secret-life-of-buildings-common-philadelphia-brick-styles/)
Sources:
http://philadelphiaencyclopedia.org/archive/row-houses/
http://www.tonerarch.com/blog/2013/6/13/your-house-and-your-facade-a-separation-agreement.html
https://www.solorealty.com/the-secret-life-of-buildings-star-bolts/
http://activerain.com/blogsview/2126096/star-bolts---they-aren-t-just-decoration-
http://structuralrepairexperts.com/tag/philadelphia-star-bolts/
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