We have spoken before about buildings, such as this 6-storey one in Paris, that were allowed to be built with only a single exit stair. This is noteworthy because, here in Canada, if you were to try and build an equivalent 6-storey building on an equivalent 100 square meter site, you would be required to have two exit stairs. And that would create more non-leasable space and make it even more challenging to develop such a small building.

It is for this reason that single-stair buildings have been getting an increasing amount of attention as of late. They are seen as a way of encouraging more missing middle housing.

So where are single-stair buildings currently allowed? Below is a map from Seattle-based Larch Lab showing the maximum number of storeys for point access blocks (what they call single-stair buildings) around the world. Based on this, Canada is one of the most conservative countries on the planet when it comes to required exiting (I don't want to speak for any of the grayed-out countries). It also shows that much of the world allows 6 or more storeys.

Larch Lab is a major advocate for point access blocks and they have this policy brief outlining the problem and the opportunities. One of their most interesting statistics has to do with minimum project size inflation. As recent as 2000, only about 13% of all multifamily completions in the US had more than 50 units. Today, this number has jumped to more than 55% of all new multifamily buildings, meaning we are quickly losing our ability to build small and intimate.

Point access blocks can help with this.

Of course, the reason we have exiting requirements in our building codes is because of life safety. But there's research to suggest that this level of redundancy may not be needed in certain buildings. According to the above policy brief, the average death rate (caused by a building) in point access block countries like Switzerland, France, Italy and Germany, is significantly lower than that of the US. On top of this, almost no countries in the EU require buildings less than 28m tall to be sprinklered. The US does.

All of this said, I don't think that single-stair buildings are a silver bullet for missing middle housing. It is just one important ingredient in a complicated recipe. And as evidence of this, we can look to Seattle. The 2018 Seattle Building Code allows point access blocks up to 6 storeys, which is a rare occurrence in the US. However, the city appears to be still working on missing middle reform. Presumably other ingredients are still -- missing.

Image: Larch Lab