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Comment by bobthepanda | Hacker News Reader

The intention of the double stairwell requirement, is that you are not supposed to have your access point to the stairwell by an obstruction, and there should be a maximum access time to the stairwell.

One notable requirement of single-stair buildings where they are legal in the US, is that

1. the height is generally determined by the height of the fire ladders available, providing a second means of egress

2. the single stair requirement usually only applies to buildings that have a low maximum units per floor. In Seattle where they are legal, this is four units. At four units a floor, your front door directly opens feet away from the stairwell, and having a second staircase a sufficient distance away would be hard to fit in the floor plan.

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> 1. the height is generally determined by the height of the fire ladders available, providing a second means of egress

This is an interesting requirement and makes me wonder if some of the need for two staircases comes from the proximity - or lack thereof - to fire services. I'd be sitting in a burning home for a long time if I had to wait for a fire ladder.

Ground fire ladders are about 35’ max. Aerial apparatus (trucks/quints) around the US are normally around 80-110 feet in length.

My current tower rig is 85’, our next will be 105.

Consider that is ladder length and the “true” height is really a hypotenuse on a right triangle with one side the building.

We can generally reach most of our properties just fine, as our tallest is about 5 stories. However there are some across a river with access harder in front, and a ladder across the river is the way to go.

A lot of the requirements make sense in bigger buildings. It's not easy to evacuate a large office building taking up a city block using only ladders. And some of it is reactive; for example, there is a distance separation requirement for stairwells, because during 9/11 the three North Tower stairwells were only 70 feet apart and enclosed only with gypsum, so they were all severed on impact, dooming the people above the impact zone. But none of this is really relevant for a building with six floors and 24 units total.

The American city topology is basically office towers surrounded by single family homes; in the midcentury we demolished a lot of the in-between building stock, which is now referred to by urbanists as the "missing middle". Compare this to Europe or Japan which is largely buildings in between those sizes.

Even Singapore has lots of those middle sized buildings missing from the US.

I think in Japanese apartment buildings they’re all required to have their own rope ladder? Since you go from balcony to balcony they don’t even have to be very long.

There's no rope ladder in my apartment here. I've never heard of such a thing.

also fire suppression system (sprinklers) and pressurized stairwells are mandated.

And fireproof walls between units. It takes a long time for a fire to penetrate two layers of drywall.

The "Well there's your problem" podcast did an episode on 'five over ones' (five stories of wood over one concrete) and touched on this - IIRC they were most likely to burn down during construction when the fire suppression wasn't installed and active yet.

They also did a more in-depth episode on Grenfell, which touched on a lot of the same issues, except Grenfell was (a) taller and (b) occupied.

I can heartily recommend that episode if you like a podcast to a) be respectful to the victims and b) clown on the people who caused it.

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