Montreal's walkup apartments

While I was in Montreal admiring the housing stock, the city's English-language Gazette happened to run an article by Christopher DeWolf explaining how it came about. See a picture of what he's talking about here, and read the article here. Relevant section:

With their distinct form - several superposed flats, each extending from the front of a building to the back - plexes are a popular form of housing, adaptable to many different lifestyles.

But what's their story? How did Montreal come to be a city of walkup apartments, outdoor staircases and balconies? (Although plexes can be found in a number of other cities, like Boston and Chicago, only in Montreal have they become so ingrained in the local culture.)

According to David Hanna, professor of geography at the Universite du Quebec a Montreal, the origins of the plex can be traced to a 19th century "marriage of convenience" between French and Scottish traditions.

Some French-Canadian settlers used outdoor staircases to link the first and second floors of their houses; immigrants from Scotland, meanwhile, brought with them the custom of stacking one flat on top of another.

"It kept morphing in the 19th century until it settled into the form of an outdoor staircase leading to each apartment," Hanna said.

I hadn't known about the stacking; I always thought all the outdoor staircases were part of the Montreal trait of refusing to accommodate the cold climate. Not only are many apartments accessible by steep staircases that are covered by snow and ice for much of the year, but almost every housing unit has a balcony or terrace facing the street (another feature considered a luxury in Boston). And I have never seen as many houses with swimming pools as I have on the bus trip from the Vermont border to Montreal. However they came about, I still think the medium-height rowhouses in Montreal are perfect for fostering vibrant neighborhoods. They provide density without casting shadows over the street, and they maximize interactions with neighbors -- unlike Boston's triple-deckers separated by driveways. But I could be romanticizing things, and maybe a Montrealer will set me right.