Brandon Donnelly

Daily insights for city builders, delivered every morning at 6 AM ET. I’m Brandon Donnelly — a Toronto-based real estate developer and founder of Globizen. I’ve been writing here since 2013.

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Tag: construction physics

  • Mail-order homes speak to a simpler time

    There was once a time — generally in the early 20th century — when some people used to order their new home from a catalogue.

    You would pick the model you wanted and then all of the required materials, along with assembly instructions, would get mailed to you.

    Mind you, this was never the most popular way to make a new home. According to Brian Potter, mail-order homes, even at their peak, represented less than 10% of all yearly housing starts in the US.

    So arguably, it was never entirely successful as a model. Building a home is tough work, especially without fancy power tools.

    Still, it’s interesting to think about its relative simplicity: “Here’s a bunch of raw building materials and some instructions. Go figure it out. It’s like an Ikea bookshelf, except it’s your entire house.”

    Contrast this to what it takes to build new urban housing today. There is a litany of new barriers. It’s nowhere near as simple as ordering a kit of parts; so it’s no wonder housing is more expensive.

    For more on “The Rise and Fall of the Mail-Order Home”, check out this recent post from Brian Potter’s Construction Physics newsletter.

  • Skyscraper construction speed by city

    Brian Potter, of Construction Physics, recently tried to determine which cities build skyscrapers the fastest.

    Here’s how he went about that:

    • He started by looking up the 50 largest cities in the world on Wikipedia
    • He then pulled data from the Council on Tall Buildings and Urban Habitat to get a list of every skyscraper completed between 2000-2020 that was over 100 meters, had a start and completion date, and had a gross floor area
    • The result was a list of 986 skyscrapers completed in 39 cities, most of which (~740) were completed in the US, China, Japan, and Canada
    • Finally, he calculated completed square feet per year and made some charts

    Here are the results:

    And here’s one thing he had to say about them:

    Interestingly enough, the huge outlier in slow construction isn’t the US, but Canada, with an average skyscraper construction speed of half that of the US’s.

    For a lot more information on this topic, click here.

  • The fall of manufactured housing

    In 1973, 580,000 mobile homes (or manufactured home as they are now called) shipped in the United States. This represented about 50% of the number of single-family housing starts that year, and about 22% of total housing starts. So they represented a significant chunk of the overall housing supply.

    But following the collapse of the US housing market in 1974, an interesting thing happened. Manufactured homes never managed to reclaim their position in the stack. See above chart. Brian Potter, author of Construction Physics, puts forward a number of possible explanations for this, over here.

    Some have speculated that it was the result of new code changes that ended up increasing costs. Some have speculated that it was because of a new requirement to include a steel chassis on the bottom of every home, which also increased costs, but more importantly stigmatized manufactured homes. It made them seem transient, whereas previously they were installed on permanent foundations.

    There are also some theories that manufactured home production was harder hit during the economic downturn given that they had more fixed plant costs (compared to site-built homes with their variable labor costs).

    But Brian’s current working theory is that it comes down to capital flows. Manufactured homes tend to cater to lower-income buyers and so supply, as the argument goes, has largely depended on “lax lending” practices being made available to them.

    I’m not so sure that this is the only reason though. For one thing, multi-family housing starts have followed a somewhat similar trajectory to manufactured homes. We’ve certainly seen an increase in supply over the last decade, but we’ve never gotten back to that early 1970’s peak.

    And so I wonder: How much of this is actually just the result of the single-family home hegemony? This is arguably what the market has historically wanted (look at the split pre-1973 in the above chart), and so perhaps we simply refocused our attention there and worked to make this housing type as accessible as possible to the masses.

    Chart via Brian Potter

  • How to tell if you have a housing shortage

    Housing supply is one of those topics that a lot of people can’t seem to agree on. Some people, including annoying city bloggers from Toronto, will tell you that we’re not building nearly enough new housing. While others will tell you that, no, everything is just fine. We are totally building enough to meet demand.

    So today I am going to encourage all of you to read Brian Potter’s latest Construction Physics article. In it, he answers the question: Is there a housing shortage or not? But just in case some of you don’t feel like doing that, here is the tl;dr:

    • You can’t look at construction rates alone and infer whether or not you have a housing shortage. There are so many other factors to consider, including household size (see above chart). A drop in household size alone, for example, means that you need more housing, even if nothing else is going on.
    • The US is probably short at least several million housing units right now.
    • Vacancy rates, within a market, are pretty useful for predicting housing cost increases. When vacancy rates fall, prices go up. This is one reason why housing supply matters.
    • Looking at the gap between population increases and housing supply increases is “hilariously non-predictive” if you’re trying to determine whether or not you need more housing. We’ve all seen this before: This city added X people, but only constructed Y new homes.
    • Finally, there is an extremely strong correlation between housing supply restrictions (i.e. land use restrictions) and home prices. It turns out that the harder we make it to build new homes, the more expensive they become.

    So yeah, Potter’s article is definitely worth a read when you get a moment.

    Chart via Construction Physics

  • A world with less concrete

    Some people like to refer to concrete as cement. But that is technically incorrect. Cement is just one of the main ingredients in concrete, along with water and aggregates. So it’s a bit like referring to a beer as a bottle of yeast.

    That said, cement is pretty integral to concrete and it’s largely the reason why the embodied carbon is so high in this widely-used building material. According to Brian Potter, cement production is responsible for somewhere between 5-10% of global CO2 emissions.

    This is coming from the roughly 4.25 billion metric tons of cement that is produced annually and the 30 billion tons of concrete that it ends up in. The world likes concrete. And in particular, China likes concrete.

    China alone is now producing about half of the world’s cement. And since consumption generally tracks production, and the consumption of cement generally translates into concrete, China is using, by far, the most concrete.

    I don’t know what the right answer is to this particular carbon problem, but Brian Potter’s latest construction physics post is perhaps a good place to start thinking about it. In it, he covers who is producing it, where it is being used, and how we might get to a world with less concrete.