# Open-air corridors and exterior exit stairs

By [Brandon Donnelly](https://brandondonnelly.com) · 2024-04-26

architecture, azure-magazine, development, efficiency-factor, egress, elevator-ratio, exit-stair, exterior-stairs, laurent-clark, low-rise-apartment, montreal, msdl-architects, suites-per-elevator

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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](https://brandondonnelly.com/2014/04/24/les-escaliers-de-montreal/) (less than five storeys). And with these, comes lots of exterior circulation. But this tradition doesn't just apply to older buildings. [Here](https://www.azuremagazine.com/article/exterior-stairs-montreal-urban-fabric-msdl-laurent-clark/?) is a contemporary tall-building example which follows a similar approach.

Designed by [MSDL Architects](https://www.msdl.ca/en/projects/laurent-clark/), the project, called [The Laurent & Clark](https://laurent-clark.com/en), 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](https://www.azuremagazine.com/article/exterior-stairs-montreal-urban-fabric-msdl-laurent-clark/?):

![](https://storage.googleapis.com/papyrus_images/baa1769cfa37ed6e43af22af8e17babb.png)

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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*Originally published on [Brandon Donnelly](https://brandondonnelly.com/open-air-corridors-and-exterior-exit-stairs)*