One of the trademarks of Tokyo's urban landscape is a lot of exterior exit stairs. For example, our hotel is almost 20 storeys and it has two exit stairs, both of which sit outside of the building. Here's a photo taken from the corridor. You can also see other buildings in the background with similar exit stair configurations.
Oftentimes these stairs will also be positioned on a building's primary elevation, making them form part of the overall architectural expression. There's no shame in doing that here. This is curious to me because it means that, on tight urban sites, you're giving up part of your frontage to egress. The alternative would be to burry it in the middle of the building and have it transfer over at some point.
In any event, my first thought when I see a lot of exterior circulation is usually that the place must have a mild climate. And indeed, this is true of Tokyo. The average January and February lows and highs are 10 degrees and 5 degrees, respectively. Snow is extremely rare here. But that doesn't seem to be what's driving this egress approach.
Because if you go up north to Sapporo, where they get upwards of 500cm of snow each year, it too has exterior exit stairs. Closer to home, there's also the example of Montreal, which is similarly known for its exterior stairs (both in its older housing stock and in some of its newer housing stock). So it can't just be a weather thing.
The more likely hypothesis is that it's simply cheaper and easier to build this way. There may also be local regulations that either directly or indirectly encourage it, beyond it just being more cost effective. Interestingly enough, though, exterior stairs don't seem to be as common in newer buildings (but this is just my anecdotal observation from the last few days).
We talk a lot these days about single-stair buildings. And I think it's clear that we need to start allowing this for larger infill projects. But Tokyo also has me wondering if we should be having a parallel conversation about more open-air exit stairs and corridors. Climate is clearly no excuse. If it can help bring down the cost of building, then it's something to consider.
The province of British Columbia made the following announcement this week:
The Province has updated the BCBC to remove the [building] code requirement for a second egress, or exit, stairwell per floor in buildings up to six storeys. This change will make it possible to build housing projects on smaller lots and in different configurations, while allowing more flexibility for multi-bedroom apartments, more density within areas of transit-oriented developments and the potential to improve energy efficiency in buildings. Previously, the BCBC called for at least two egress stairwells in buildings three storeys and higher.
This is meaningful progress. And BC is the leading the way in Canada. But from a global perspective, we are not leading the way. This is us catching up.
As part of this building code change, the province commissioned a report on single egress stair building designs. In this report, they looked at various jurisdictions from around the world:
Their non-exhaustive findings:
There are at least 30 jurisdictions with SES building design requirements that permit midrise buildings with a building height of at least 5 or 6 storeys. In addition, the Center for Building in North America (www.centerforbuilding.org) reports that 8 US states have passed legislation into law, or are reviewing possible options for doing so, to allow larger SES buildings when their Building Code is next revised. In most cases these revisions are intended to allow SES buildings of up to 6 storeys.
For example, Seattle already allows up to 6 storeys. Belgium, New Zealand, and Australia allow up to 9 storeys (driven by a maximum height in meters). And Finland allows up to 18 storeys, according to the report.
Though keep in mind that building codes are complicated and often have frustrating gray areas. There may be other requirements that need to be met in order to achieve these heights.
It's great to see BC making these moves. Now watch for other provinces to follow suit.
Montreal is, in many ways, a city of winding exterior stairs. If you've been there, then you know. The city is overwhelmingly a city of low-rise apartments (less than five storeys). And with these, comes lots of exterior circulation. But this tradition doesn't just apply to older buildings. Here is a contemporary tall-building example which follows a similar approach.
Designed by MSDL Architects, the project, called The Laurent & Clark, consists of two tower volumes. They read as two separate towers, but they're connected and share egress paths. On the east side is a conventional "scissor stair" tucked behind two elevators. And on the other end, connected by an open-air corridor, is an exterior exit stair that runs all the way up the tower.
Here is a circulation diagram via Azure:
This is novel (at least in this part of the world). The suites in the west tower are all dual aspect; meaning, they have windows on both ends.
They also have direct elevator access (see cores above), which means a lot less non-revenue generating circulation space. I mean, if you think about it, the open-air corridor on the north side of the west tower is akin to building a simple balcony. Extend the slab and add a guard rail. And so you could argue that this portion of the building has a near 100% efficiency factor.
However, the downside is that you need more elevators. Here, it looks like they have 6 for their 356 suites. That's an overall ratio of just under 60 suites per elevator, which is lower (i.e. better) than what you'd typically find in a conventional tower. The crude rule of thumb is 1 elevator for every 100 suites. That said, these direct-access suites would be premium.
But perhaps the most important takeaway is this: If cold and snowy Montreal is cool with open-air corridors and exterior exit stairs, then maybe your city should be as well.
One of the trademarks of Tokyo's urban landscape is a lot of exterior exit stairs. For example, our hotel is almost 20 storeys and it has two exit stairs, both of which sit outside of the building. Here's a photo taken from the corridor. You can also see other buildings in the background with similar exit stair configurations.
Oftentimes these stairs will also be positioned on a building's primary elevation, making them form part of the overall architectural expression. There's no shame in doing that here. This is curious to me because it means that, on tight urban sites, you're giving up part of your frontage to egress. The alternative would be to burry it in the middle of the building and have it transfer over at some point.
In any event, my first thought when I see a lot of exterior circulation is usually that the place must have a mild climate. And indeed, this is true of Tokyo. The average January and February lows and highs are 10 degrees and 5 degrees, respectively. Snow is extremely rare here. But that doesn't seem to be what's driving this egress approach.
Because if you go up north to Sapporo, where they get upwards of 500cm of snow each year, it too has exterior exit stairs. Closer to home, there's also the example of Montreal, which is similarly known for its exterior stairs (both in its older housing stock and in some of its newer housing stock). So it can't just be a weather thing.
The more likely hypothesis is that it's simply cheaper and easier to build this way. There may also be local regulations that either directly or indirectly encourage it, beyond it just being more cost effective. Interestingly enough, though, exterior stairs don't seem to be as common in newer buildings (but this is just my anecdotal observation from the last few days).
We talk a lot these days about single-stair buildings. And I think it's clear that we need to start allowing this for larger infill projects. But Tokyo also has me wondering if we should be having a parallel conversation about more open-air exit stairs and corridors. Climate is clearly no excuse. If it can help bring down the cost of building, then it's something to consider.
The province of British Columbia made the following announcement this week:
The Province has updated the BCBC to remove the [building] code requirement for a second egress, or exit, stairwell per floor in buildings up to six storeys. This change will make it possible to build housing projects on smaller lots and in different configurations, while allowing more flexibility for multi-bedroom apartments, more density within areas of transit-oriented developments and the potential to improve energy efficiency in buildings. Previously, the BCBC called for at least two egress stairwells in buildings three storeys and higher.
This is meaningful progress. And BC is the leading the way in Canada. But from a global perspective, we are not leading the way. This is us catching up.
As part of this building code change, the province commissioned a report on single egress stair building designs. In this report, they looked at various jurisdictions from around the world:
Their non-exhaustive findings:
There are at least 30 jurisdictions with SES building design requirements that permit midrise buildings with a building height of at least 5 or 6 storeys. In addition, the Center for Building in North America (www.centerforbuilding.org) reports that 8 US states have passed legislation into law, or are reviewing possible options for doing so, to allow larger SES buildings when their Building Code is next revised. In most cases these revisions are intended to allow SES buildings of up to 6 storeys.
For example, Seattle already allows up to 6 storeys. Belgium, New Zealand, and Australia allow up to 9 storeys (driven by a maximum height in meters). And Finland allows up to 18 storeys, according to the report.
Though keep in mind that building codes are complicated and often have frustrating gray areas. There may be other requirements that need to be met in order to achieve these heights.
It's great to see BC making these moves. Now watch for other provinces to follow suit.
Montreal is, in many ways, a city of winding exterior stairs. If you've been there, then you know. The city is overwhelmingly a city of low-rise apartments (less than five storeys). And with these, comes lots of exterior circulation. But this tradition doesn't just apply to older buildings. Here is a contemporary tall-building example which follows a similar approach.
Designed by MSDL Architects, the project, called The Laurent & Clark, consists of two tower volumes. They read as two separate towers, but they're connected and share egress paths. On the east side is a conventional "scissor stair" tucked behind two elevators. And on the other end, connected by an open-air corridor, is an exterior exit stair that runs all the way up the tower.
Here is a circulation diagram via Azure:
This is novel (at least in this part of the world). The suites in the west tower are all dual aspect; meaning, they have windows on both ends.
They also have direct elevator access (see cores above), which means a lot less non-revenue generating circulation space. I mean, if you think about it, the open-air corridor on the north side of the west tower is akin to building a simple balcony. Extend the slab and add a guard rail. And so you could argue that this portion of the building has a near 100% efficiency factor.
However, the downside is that you need more elevators. Here, it looks like they have 6 for their 356 suites. That's an overall ratio of just under 60 suites per elevator, which is lower (i.e. better) than what you'd typically find in a conventional tower. The crude rule of thumb is 1 elevator for every 100 suites. That said, these direct-access suites would be premium.
But perhaps the most important takeaway is this: If cold and snowy Montreal is cool with open-air corridors and exterior exit stairs, then maybe your city should be as well.
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