Unaffordability has apparently gotten so bad that we are now seeing a groundswell of support for increasing overall housing supply. So politicians are doing things. And this week, the Province of British Columbia proposed some new legislation related to transit hubs.
As proposed, the legislation will require BC municipalities to designate Transit Oriented Development Areas (TOD Areas), mandate minimum heights and densities within certain radii (broadly 800m in the case of rapid transit stations), and remove parking minimums.
Not surprisingly, a lot of people are excited about this and, there's no question, that this is directionally the right thing to do. But I have two immediate thoughts.
The first is that the devil is always in the details. This all sounds good, but: Are the proposed minimum densities and heights going to be enough to stimulate development? For example, is 4 the right minimum FAR for 300m from a transit station?
The second thought has to do with the level of excitement surrounding this announcement. (I'm going strictly based on Twitter, which admittedly could just be my bubble). The fact that city builders are so excited about this announcement tells us a lot about the current state of affairs.
Unaffordability has apparently gotten so bad that we are now seeing a groundswell of support for increasing overall housing supply. So politicians are doing things. And this week, the Province of British Columbia proposed some new legislation related to transit hubs.
As proposed, the legislation will require BC municipalities to designate Transit Oriented Development Areas (TOD Areas), mandate minimum heights and densities within certain radii (broadly 800m in the case of rapid transit stations), and remove parking minimums.
Not surprisingly, a lot of people are excited about this and, there's no question, that this is directionally the right thing to do. But I have two immediate thoughts.
The first is that the devil is always in the details. This all sounds good, but: Are the proposed minimum densities and heights going to be enough to stimulate development? For example, is 4 the right minimum FAR for 300m from a transit station?
The second thought has to do with the level of excitement surrounding this announcement. (I'm going strictly based on Twitter, which admittedly could just be my bubble). The fact that city builders are so excited about this announcement tells us a lot about the current state of affairs.
Because what this proposed legislation is more or less saying is the following: "Hey, here's a great idea! Let's build more housing around higher order transit and not force the market to build unnecessary parking."
Is this really something that should be considered novel? I thought this was just how cities should work.
As I mentioned yesterday, I am not a structural engineer. However, my friend James Cranford is. He is Principal at Stephenson Engineering and he was nice enough to answer a few of my questions about soft story buildings (storey if you're Canadian).
BD: What is a soft (or weak) storey building? And why is it such an important design challenge, even in a very un-seismic city like Toronto?
JC: A soft storey refers to any level in a building that has LESS capacity than the level above. This means it has both less strength to resist loads and less stiffness so that it will move more than the levels above. Soft stories are one of the most significant challenges that many modern building designers face because they are one of the most likely ways that a building can fail catastrophically if not properly designed. A soft storey failure occurs when the building hinges above the weak level and the columns below can no longer support the load of the building above as they become overstressed and loaded in ways they were never meant to act. This leads to a sudden, often pancake type collapse that is likely to bring down the entire building.
I am a big fan of Victoria-based developer Aryze. And their Pearl Block project is a good example of why. Developed on an awkward triangular lot that had been sitting vacant for nearly 65 years and that presumably every other developer had been overlooking, the project brought six family-oriented townhouses to the Oaklands neighborhood of Victoria, BC.
Because what this proposed legislation is more or less saying is the following: "Hey, here's a great idea! Let's build more housing around higher order transit and not force the market to build unnecessary parking."
Is this really something that should be considered novel? I thought this was just how cities should work.
As I mentioned yesterday, I am not a structural engineer. However, my friend James Cranford is. He is Principal at Stephenson Engineering and he was nice enough to answer a few of my questions about soft story buildings (storey if you're Canadian).
BD: What is a soft (or weak) storey building? And why is it such an important design challenge, even in a very un-seismic city like Toronto?
JC: A soft storey refers to any level in a building that has LESS capacity than the level above. This means it has both less strength to resist loads and less stiffness so that it will move more than the levels above. Soft stories are one of the most significant challenges that many modern building designers face because they are one of the most likely ways that a building can fail catastrophically if not properly designed. A soft storey failure occurs when the building hinges above the weak level and the columns below can no longer support the load of the building above as they become overstressed and loaded in ways they were never meant to act. This leads to a sudden, often pancake type collapse that is likely to bring down the entire building.
I am a big fan of Victoria-based developer Aryze. And their Pearl Block project is a good example of why. Developed on an awkward triangular lot that had been sitting vacant for nearly 65 years and that presumably every other developer had been overlooking, the project brought six family-oriented townhouses to the Oaklands neighborhood of Victoria, BC.
We see potential soft storey issues most commonly in mid to high-rise residential buildings that have either amenity or retail spaces at the ground floor. These are spaces that by nature are large and as open as possible. During design, the structural engineer needs to recognize this and compensate for the lost capacity in other ways. This is usually done through a combination of increasing the capacity of the remaining walls and adding new walls at the weak level that fit with the building layouts.
BD: What does the Ontario Building Code mandate in terms of soft storeys?
JC: The OBC generally does not permit soft stories in any form for buildings where people are likely to live, work or play. In critical infrastructure like hospitals which must remain fully functional in the event of a major earthquake, the OBC goes further and does not permit any ‘lateral force resisting elements’ like shear walls or steel frames to be discontinuous below. This means that if you have a wall on the 5th floor of a hospital, that wall must exist with equal or greater capacity on EVERY level below, without exception.
BD: How much more stringent is British Columbia, where there is greater seismic risk?
JC: The requirements in the British Columbia Building Code (BCBC) are almost identical to those in Ontario in this case. However, the seismic design forces will be much higher based on the potential for much larger earthquakes, so while buildings will generally be designed for a higher seismic capacity, they must be proportioned similarly to prevent soft stories.
BD: Speaking generally, what is usually required structurally in order to retrofit an existing soft storey building so that it can properly withstand things like earthquakes?
JC: The most common way to retrofit a soft-storey is to increase the capacity of the weak level. In smaller buildings this can usually be achieved by adding new ‘lateral-force-resisting elements’ like shear walls or moment/braced frames until the overall storey capacity matches or exceeds the capacity of the levels above. On larger buildings this becomes more complex, as the loads are much higher and simply adding capacity may not be either feasible or practical. Therefore a full structural analysis is usually required to find a solution that can be tailored to the unique structural and architectural conditions. This often involves a combination of increased capacity and the introduction of ductile detailing which will allow the building to dissipate seismic energy. This can be roughly thought of as a ‘bend but don’t break’ approach to surviving an earthquake.
In some jurisdictions, the extreme risk caused by (many) homes built with soft stories has prompted local governments to intervene. The City of San Francisco (as well as many other municipalities in California) have enacted ordinances requiring home owners to assess and upgrade their properties, including single family home with garages a the lowest level, to reduce the risk of soft-storey failure in an earthquake.
BD: Thanks for this, James.
I don't usually do Q&As on this blog, so let me know in the comment section below if you found this one valuable and if you'd like to see more of them.
Each of the towns has 3 bedrooms. Each has a living room facing the street (but with privacy from the neighbor). Each has a large rooftop deck (with 5 foot parapet walls so no kids fall over). And according to the developer, each sold for less than the average price of a single-family home in the Oaklands area. Not surprisingly, the project also won all sorts of awards.
It is a great example of the kind of beautiful and mid-market missing middle housing that so many of us are always talking about. Why build 1 home when you can build 6? Why build 6 homes when you can build 18? Still, there remains far too many obstacles in the way of any sort of housing that doesn't conform to the status-quo:
It shouldn't be this difficult. And it shouldn't take this long. Actually, let me rephrase this. It can't be this difficult and it can't this long; that is, if we're expecting to actually come close to meeting the demand for new housing. There is no great mystery as to why the missing middle is, you know, missing. We made it that way.
We see potential soft storey issues most commonly in mid to high-rise residential buildings that have either amenity or retail spaces at the ground floor. These are spaces that by nature are large and as open as possible. During design, the structural engineer needs to recognize this and compensate for the lost capacity in other ways. This is usually done through a combination of increasing the capacity of the remaining walls and adding new walls at the weak level that fit with the building layouts.
BD: What does the Ontario Building Code mandate in terms of soft storeys?
JC: The OBC generally does not permit soft stories in any form for buildings where people are likely to live, work or play. In critical infrastructure like hospitals which must remain fully functional in the event of a major earthquake, the OBC goes further and does not permit any ‘lateral force resisting elements’ like shear walls or steel frames to be discontinuous below. This means that if you have a wall on the 5th floor of a hospital, that wall must exist with equal or greater capacity on EVERY level below, without exception.
BD: How much more stringent is British Columbia, where there is greater seismic risk?
JC: The requirements in the British Columbia Building Code (BCBC) are almost identical to those in Ontario in this case. However, the seismic design forces will be much higher based on the potential for much larger earthquakes, so while buildings will generally be designed for a higher seismic capacity, they must be proportioned similarly to prevent soft stories.
BD: Speaking generally, what is usually required structurally in order to retrofit an existing soft storey building so that it can properly withstand things like earthquakes?
JC: The most common way to retrofit a soft-storey is to increase the capacity of the weak level. In smaller buildings this can usually be achieved by adding new ‘lateral-force-resisting elements’ like shear walls or moment/braced frames until the overall storey capacity matches or exceeds the capacity of the levels above. On larger buildings this becomes more complex, as the loads are much higher and simply adding capacity may not be either feasible or practical. Therefore a full structural analysis is usually required to find a solution that can be tailored to the unique structural and architectural conditions. This often involves a combination of increased capacity and the introduction of ductile detailing which will allow the building to dissipate seismic energy. This can be roughly thought of as a ‘bend but don’t break’ approach to surviving an earthquake.
In some jurisdictions, the extreme risk caused by (many) homes built with soft stories has prompted local governments to intervene. The City of San Francisco (as well as many other municipalities in California) have enacted ordinances requiring home owners to assess and upgrade their properties, including single family home with garages a the lowest level, to reduce the risk of soft-storey failure in an earthquake.
BD: Thanks for this, James.
I don't usually do Q&As on this blog, so let me know in the comment section below if you found this one valuable and if you'd like to see more of them.
Each of the towns has 3 bedrooms. Each has a living room facing the street (but with privacy from the neighbor). Each has a large rooftop deck (with 5 foot parapet walls so no kids fall over). And according to the developer, each sold for less than the average price of a single-family home in the Oaklands area. Not surprisingly, the project also won all sorts of awards.
It is a great example of the kind of beautiful and mid-market missing middle housing that so many of us are always talking about. Why build 1 home when you can build 6? Why build 6 homes when you can build 18? Still, there remains far too many obstacles in the way of any sort of housing that doesn't conform to the status-quo:
It shouldn't be this difficult. And it shouldn't take this long. Actually, let me rephrase this. It can't be this difficult and it can't this long; that is, if we're expecting to actually come close to meeting the demand for new housing. There is no great mystery as to why the missing middle is, you know, missing. We made it that way.
