Sidewalk Vault Lights

One of the few remaining sidewalk vault light panels in Butte, Montana, 2013.

One of the few remaining sidewalk vault light panels in Butte, Montana, 2013.

Invented in 1845 by Thaddeus Hyatt, sidewalk vault lights started being used in urban areas beginning around the 1850s and continued to be popular into the 1930s. The first vault lights were engineered to have glass blocks placed into a cast-iron framework. Later, with the introduction of Portland cement, setting them into reinforced concrete panels was more common.

Sidewalk vault light panels in San Francisco, California, 2015. This is one of the most intact panels I have ever seen.

Sidewalk vault light panels in San Francisco, California, 2015. This is one of the most intact panels I have ever seen.

Thaddeus Hyatt's Pendant Lens Patent illustrating how the light is distributed.

Thaddeus Hyatt’s Pendant Lens Patent illustrating how the light is distributed.

These “lights” provided a way to get light into the useful basement and void areas under the sidewalks. This also made the space rentable in some cases. First attempts at vault lights proved unfruitful because the design basically allowed a single shaft of light to shine straight down into the space below. With Hyatt’s invention, the design incorporated a prism shape (“saw-tooth”) on the underside while the surface above remained smooth to walk across. This provided a way for the light to be directed over a broader area in the dark underground.

Brown Bros. Manufacturing Co. catalog advertising the "Hyatt" refracting lens. Sidewalk vault technology was primarily geared toward business owners in urban areas.

Brown Bros. Manufacturing Co. catalog advertising the “Hyatt” refracting lens. Sidewalk vault technology was primarily geared toward business owners in urban areas.

Faced with the pressure of typical sidewalk use over the years, many glass blocks have been broken and loose seals have caused them to fall out entirely. For obvious reasons, this creates hazardous walking conditions as well as allow water and other debris into the space below. Yet repairing virtually unnecessary sidewalk vault lights can be considered costly and challenging when compared to the simple solution of removing or covering them with asphalt or concrete. The need for an experienced contractor and locating supplies and fabricators for the glass blocks and sometimes the cast-iron panels are not the only challenges. Today building code and load requirements are quite different from the 19th and early 20th centuries; especially when taking into consideration that the void space under the deteriorated sidewalk lights might need structural work as well.

A glass "saw-cut" block from a sidewalk vault light panel in Missoula, Montana, 2012.

A glass “saw-cut” block from a sidewalk vault light panel in Missoula, Montana, 2012.

However, repair and maintenance of these beautiful architectural features is not as difficult and expensive as it may seem. Restoration projects in various urban areas show that, “sensitively rehabilitated vault lights can continue to provide architectural and historic character to the urban streetscape while serving their original function of naturally illuminating basement spaces” (Stachelberg and Randl, 2003).

Stachelberg, Cas, and Chad Randl                                                         2003 Historic Glass Number 2: Repair and Rehabilitation of Historic Sidewalk Vault Lights, Preservation Tech Notes National Park Service U.S. Department of the Interior, Washington D.C.

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