Have you ever been walking in an older part of Vancouver and noticed a checkerboard grid of purple glass squares under your feet? They’re not simply sidewalk decoration, though wouldn’t that be nice! They’re called sidewalk prisms, and they once served an important purpose.
In the late 19th and early 20th centuries they were a means to illuminate spaces under sidewalks called areaways. Sidewalk prisms, also known as vault lights (or pavement lights in the UK), are glass prisms set into sidewalks in order to reflect natural light from above, illuminating the subterranean spaces.
I first wrote about sidewalks prisms on my blog, vanalogue, in 2016, but my fascination with them began many years before that. It was back in the 70s as a child obsessed with all things purple that I first noticed those “purple glass squares” embedded in Vancouver’s sidewalks.
Many of the buildings built during Vancouver’s economic boom in the years prior to the First World War included sidewalk prisms. Once an omnipresent part of the urban streetscape, their numbers have diminished significantly during my lifetime.
The concept for these areaway “lights” came from a similar system used on ships, starting in the middle of the 19th century. Deck prisms were used to safely illuminate the cargo hold by bringing in light without the use of candles – which could prove very hazardous on a wooden ship, especially if it was carrying flammable or explosive cargo. Later in the century, this system of illumination was adapted for city use, and the sidewalk prism was born.
What are areaways? They are excavated, below-grade spaces around the walls of a building designed to afford access, air and light to a basement. Justine Murdy explained in an interesting article that ever since Vancouver’s incorporation in 1886 property owners in the downtown area (i.e. the CBD, Gastown, Chinatown) were charged “taxes for sidewalks that aligned with their lots, even though using the space above the sidewalk wasn’t permitted”. Some property owners took advantage of this regulation and decided to use the spaces below the sidewalks to expand their basements. As Murdy explains: “by paying a minimal encroachment fee to the City, basements could be extended into the area under the sidewalk” past the building wall up to the street wall. By the time areaways came into use in Vancouver, many cities in North America as well as the UK were already using glass prisms to safely illuminate these spaces. The idea of lighting otherwise dark and dank areas with “pure, healthful, white light from wall to wall” was very appealing in the Victorian and Edwardian eras.
Why are the glass blocks purple? That’s from the manganese added (ironically, as a decolourizer) to glass formulas in the 19th and early 20th Centuries. Exposed to UV light or sunlight, the manganese turned a purple or amethyst hue over time. The amount of manganese added to the prisms determined how deep a purple colour the “solarized glass” would turn.
As Vancouver grew, so did city infrastructure needs. Since regular access to utilities (sewer, waterworks, electrical etc.) was required, it made more sense for the City to use the space under the sidewalk, rather than the street (which would disrupt traffic) to run and access these utilities. At the same time, businesses were shifting away from using coal as their main heating source. Soon, all those coal chutes leading into areaways and basements below ground were no longer needed. In some cases, areaways were taken over by the City for its own use.
The second half of the 20th Century also saw a lot of “modernization” in the city, resulting in new building projects. With them came new sidewalks, resulting in the loss of active areaways and sidewalk prisms. New safety regulations from the City of Vancouver Engineering Department also forced the closure of areaways – the sidewalk above had to be able to withstand the weight of an emergency vehicle parked on it. Areaways were filled in either permanently with cement or semi-permanently with gravel. Such is the case of Gastown’s historic Hotel Europe — the areaways beneath its sidewalks that once housed, among other things, a saloon, are now sadly filled with gravel.
Sidewalk prisms are not just square shaped, but also can be round and lozenge shaped and are found regionally in many west coast cities, such as Victoria, Seattle, Portland, and San Francisco. On a recent trip to the “City by the Bay” I was pleased to find several fine examples of historic sidewalk prisms (or vault lights, as they were called in the US) including these (see below) outside the aptly named “City Lights” bookstore.
The best part of this discovery was being able to go inside the ca.1907 building and see the prisms from below. I was surprised to find that even though they were tinged purple, they actually let in quite a bit of light.
Since I seemed to come across those “purple glass squares” less and less over the years, my fear was that they were disappearing faster than I thought. I wondered just how many examples were still around in Vancouver. With a little research, I found this art-based vault lights (aka sidewalk prisms) map by Samantha Knopp. On her stylized map, she identified 12 locations of vault (or prism) lights in the city. This map provided jumping off points for my own discoveries.
Sidewalk prism lights have historically fallen through the heritage preservation cracks (no pun intended). They give our streets character and are part of our built heritage. Any original examples left should be preserved, as they are rare historical facets of our urban landscape. Architectural heritage advocates such as Donald Luxton encourage and inform heritage property owners on the history of sidewalk prisms and their need for preservation. Ultimately it’s up to the owners to foot the bill, according to city rules. In many cases the costs involved to preserve these features are untenable without special funding. Fortunately, there are several recent examples of restored sidewalk prisms that were included in building restoration projects. It would be great fun if some of these new prisms actually turned purple over time.
Recently, I’ve been noticing the occasional nod to Vancouver’s sidewalk past with new building developments. Modern interpretations include square grid patterns in the concrete or even contrasting squares embedded in the sidewalk. Take, for example, the sidewalk outside The Crossroads development at Broadway & Cambie (pictured above); there’s no denying that these glassy, green squares are reminiscent of the sidewalk prisms of the past!
I decided to create my own detailed map of the sidewalk prisms of Vancouver, primarily to determine the current state of sidewalk affairs. This interactive map is the result of many hours spent researching, walking around the city, and refining the original map I created in 2016. To date, I’ve located 17 examples of sidewalk prisms in Vancouver. I hope you use it for your historical explorations, a let me know in the comments if I’ve missed any.