Unlike some building codes, this one is directly connected to a life and death issue and we have seen what happens in fires where people can’t get out.
"Zeidler explains that “this appears to be a reasonable precaution for life safety. However, the life safety of this single stair type in Europe has been equal to, if not better than ours,” due to the fact that the single stair scheme is shared between fewer units."
And that's the thing, entire countries disagree on the necessity of a second stairwell for fire safety, and there's data to back up the position.
But because a lot of people in North America have those (unfounded) fears, the second stairwell is part of the building code, and as a result an entire class of buildings don't get built because the economics don't work out.
And in low rise buildings, there's usually a LOT of stairways lol. A typic suburban US apartment complex has a half dozen buildings, and each one has maybe 12 apartments and like 4 stairways.
https://www.treehugger.com/single-stair-buildings-united-sta...
I don't believe the fears are unfounded, and frankly I don't see why anyone should buy what this Zeidler guy is selling -- if what he is saying is true, all it means is that European buildings should also be changed to have multiple egress options for every unit!
Seriously, would you be willing to live on the 6th floor of a building where the only way out in a fire is a single staircase? Don't look at statistics to decide this: even if you would be safe most of the time, it only takes one outlier incident to kill you, so why put yourself in that situation?
I think the argument is: adding a second staircase means creating a large hallway, which might make it easier for the fire to spread.
I don't see why we shouldn't look at statistics. If something is statistically safer, wouldn't we want that?
Perhaps it can be compensated for with various "either two egresses OR each bedroom must be equipped to be fire proof for X minutes" or something, and bring back hook and ladder trucks (arguably which are not used as much because buildings now have multiple egresses when that tall).
This is the kind of absurdly complex regulation that sounds simple, but is a lobbyist's dream. Two exits are easy to know when you've implemented, and easy for regulators to check if you've implemented. A "bedroom" being "fire proof" for X minutes will involve 900 pages of nonsense regulations from which lobbyists have carefully removed anything that will affect their bottom line.
"Each bedroom must be equipped to be fire proof for X minutes" was the type of rule that caused the fire brigades to tell people in Grenfell to stay in their apartments, and even more importantly the type of rule that allowed contractors to claim compliance to was sufficient enough that they could use flammable, shit cladding that was illegal in Europe and the US, and install it incompetently (because if the units were "fireproof," who could care?)
When you have a 99% chance of things going well, and a 1% chance of things going badly, normally you would feel very safe. But when “things going badly” can mean dozens or hundreds of people dying in a fire, that 1% suddenly looks a lot more serious.
Besides Grenfell, the same thing (without deaths, thankfully) happened in Milan (very similar issue with aluminium panels on the outside):
https://www.youtube.com/watch?v=iNvbxTMSM5Y
What emerged from both these fires is that some of the "new" materials are far less safe than expected and that the fire brigades simply have no means to pump water at a height more than a few floors (ten-twelve?).