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Comment by Abroszka | Hacker News Reader

Is it because of the building materials used? I think wood is super common in the US and wood burns easily. If one flat catches fire, all of them do.

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Wood is very common in single story houses in the US. Large apartment buildings are made of concrete and steel. The tallest wood framed project I've seen was 3-4 stories with the first two concrete.

Fire codes were recently changed and now buildings with 4 or 5 wooden floors are becoming common:

https://en.m.wikipedia.org/wiki/5-over-1

> 5-over-1 buildings often feature secure-access interior hallways with residential units on both sides, which favors a U, E, C, or right-angle building shape.

This is a fascinating thing for me, and it makes me want to truly study architecture. Though, like so many pieces of art and society, America my home seems to be sliding further from anything that doesn't optimize for money, or... optimization.

But the idea of code defining form, and how we can meld safety, efficiency and beauty together - that's interesting to me.

I found this article [1] on the wiki page of 5-over-1 and find it hilarious. It's an interesting and biting critique of a number of styles that are applied to 5-over-1. I wonder if we will ever have again in this country truly beautiful housing for the masses, or if we will look back on the 2000s and 2010s US as we do now, looking at Soviet bloc apartments from the 60s and 70s.

https://www.westword.com/arts/denver-is-drowning-in-awful-ar...

There’s plenty of old architecture that is utilitarian and for the poor. I think much of our romanticism for old architecture in the US is seen though the lens of survivorship bias. Construction in the US is fairly cheap and we tear down things down often, especially if it’s ugly. I’d rather look at the average US 5-over-1 than a Spanish corrala

The fire risk has very little to do with the material itself, and everything to do with how it's used. Steel buildings can fail even faster than wood once the steel reaches a superheated temperature, and wood can take an exceptionally long time to burn depending on multiple factors, from thickness, to oxygen, to fire travel pathways, to fireproof paneling.

The reason residential buildings are constructed with a given material is usually due to the regional cost of each material. Wood is cheap and plentiful in the USA, and we've adapted it very successfully with modern building codes. But of course that cost changes with scale, as wood is not nearly as strong and light as steel, or as stiff and compressive as concrete. And our somewhat antiquated zoning laws also limit newer construction methods like post-and-beam, which results in larger, cheaper, faster to construct wood-framed homes.

It's primarily because you can't easily foresee at the time you design the building where any/all future fires will occur.

If the stairway's the only way out and that's where a fire happens, then the whole thing is a deathtrap.

It's not just "fire in the stairway" that's a problem.

A number of high-fatality fires in structures over the years have involved a fire in one part of the building using an open stairway as a chimney to both fan the flames and to spread between levels. That's part of why the US stairways generally have fire doors that will "fail closed" at any fire alarm - by having the doors all closed, and (often) a ventilation system that overpressures stairwells somewhat, you have a clear space to evacuate, and, at worst, doesn't actively help the fire.

The alternative is that as a fire progresses on a lower level, the hot gasses find an open stairwell and head up, quite rapidly. The air coming in to replace this is effectively a forced draft for the fresh fire, and the hot gasses going up rapidly end up hot enough to start igniting things on other levels, in addition to making the stairwell totally unusable for evacuation. If you're unlucky, a well placed stairwell with a skylight that rapidly breaks from heat can turn a first floor fire into, quite literally, a very effective furnace with exceedingly poor containment.

This effect, unfortunately, has been demonstrated at great loss of life in various school fires and such over the years. https://en.wikipedia.org/wiki/Collinwood_school_fire is one such, but there have been quite a few others over the years as well.

As much as it may be architecturally unpopular, the stairwell requirements in US buildings are one of those "written in blood" regulations that have very good historical evidence for why they exist.

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