Photographer Michael Wolf died at his home in Hong Kong this week. He was 64. Even if you don't recognize the name, I am sure that many of you have seen his work. Perhaps his most famous project was "Architecture of Density", which had him documenting Hong Kong's extreme urban density from 2003 to 2014. Here is a photo (taken from his website):

Michael was born in Germany, but grew up in Canada (he went to school in midtown Toronto) and in the United States. He eventually settled in Hong Kong and Paris -- both of which became muses for his work. Michael made a career out of documenting cities and the life that happens within them. If you aren't familiar with his work, I would encourage you to check it out here.

Photo: Michael Wolf

Witold Rybczynski's recent post about the tragic fire at Notre-Dame de Paris provides an interesting summary of cathedral construction techniques over the years:

The Paris fire is also a reminder of what a weird hybrid structure Gothic cathedrals really are. The ancient Romans roofed their basilicas and baths with concrete vaults (the Pantheon with a dome), and the Byzantines used thin domes and vaults of brick. Over time, builders lost these skills and Romanesque cathedrals were roofed with exposed timber rafters like big barns. This made the buildings highly susceptible to fire, often caused by lightning strikes. The solution, pioneered at Durham Cathedral in the 11th century, was to build a lightweight ribbed stone vault over the nave. The timber roof remained, so the vault had no structural function (except to support itself) but it separated the interior from the flammable roof above. This was largely effective as the April 15 fire shows.

Below is an image from the WSJ depicting Notre-Dame's timber rafters and showing the extent of the area consumed by the fire. Fortunately, relatively little of the cathedral was actually destroyed.

Going forward, there will almost certainly be a debate about how the roof and spire should be rebuilt. What materials and construction methods are appropriate for this emblem of Christianity and French culture?

But I agree with Witold in that "there is nothing inauthentic about rebuilding."

It is common to lament that buildings simply aren't built like they used to be. But this is not a new phenomenon. Construction methods change, as do the skills of builders.

There may have been critics in the 1220's complaining about how the cathedral's roof was built using wood, instead of concrete or brick vaulting. But that's what was relevant at the time.

We also know that there have been periods of time since its construction where Notre-Dame simply languished. In fact, some have argued that this week's fire was the result of decades of neglect.

But Victor Hugo once wrote that, “great buildings, like great mountains, are the work of centuries." Despite what unfortunately happened this week, that remains true of Notre-Dame de Paris.

As I wrote about last month in this pithy post, the relationship between building height and density are often misunderstood. They mean different things and so the implications for our cities can also be vastly different.

I woke up this morning to a couple of tweets by John Michael McGrath that I think hit the nail on the end with respect to this duality. If you can't see them below, click here.

Paris is known, and largely celebrated, for its "European-scaled" mid-rise buildings. But as John points out, these buildings often line narrow streets (see above). They are typically also built across large blocks with compact internal courtyards and with few setbacks and/or stepbacks. The combined result is that Paris is one of the densest cities in Europe. It has mid-rise at scale.

The North American context is quite different. The large majority of our land is usually reserved for low density housing. (Here in Toronto this land has been nicknamed the "Yellowbelt.") We have a policy context that only allows intensification in select places, and that can create pressures to build up. It's a bit like squeezing a closed tube of toothpaste.

In 2012, Eurostat ranked Paris as the densest city in Europe with an average population density of approximately 21,516 people per square kilometer. Whereas, according to Wikipedia, the population density of metro Toronto was around 5,905 people per square kilometer in 2016.

What is it, again, that we love so much about Paris?