Star-shaped earthquake bolts

Frequently, I overhear Charleston tour guides telling their guests about the small, metal bolts on most of the old buildings around town. Some have a simple, circular shape, while others are intricate, star shapes (right).

Most people are unaware that Charleston lays on a fault line, and the city experienced massive damage from an earthquake in 1886. After this quake, builders began installing pattress bolts, or earthquake bolts as it is commonly referred to in Charleston, to strengthen their buildings.

Earthquake bolts are made up of two parts–an iron rod and a plate (or bolt). The plates are the visible element of the support structure that are seen on the outside of building. Cigar Factory’s Superintendent Jeff Barber of Trident Construction explains, “These plates are connected to a rod that penetrates the exterior of the building and then bolted to the timber frame on the interior of the building. This, in effect, literally bolts the exterior masonry to the structural timber frame of the building.”

Cigar Factory currently has 12 bolts, and work has begun to add 300 earthquake bolts to the face of the building. The process should take a few weeks.

Bolts are connected to a rod (above) that penetrates the exterior of a building and then bolted to the timber frame on the interior of the building.

Plates (or bolts) being painted before installation. They will connect to the rods above.