Twenty feet wide and fourty feet long is like 6x12 meters per floor.

That’s as big as my entire house, and we can fit 4 rooms, a kitchen and a bathroom in there.

2.5 rooms per floor would be the height of luxury.

Why do you say these are terrible?

I would say it because I've spent time on crutches, I have a parent in a wheelchair and another one that just wouldn't have the energy for a staircase much of the time, and staircases are a pain in the neck with small children and make it harder to move appliances and large items of furniture in and out. As a default form of housing, living across four floors is actively excluding many people with disabilities and massively reduces the ability of aging seniors to manage unassisted living.

These sound like complaints against any house with stairs. I think that disqualifies like 95% of all stock regardless.

I think we’d find that the number of people that need single floor apartments fairly closely follows the available supply.

If the first floor apartment had ramp access then wheelchairs could get in. Elevators are another option but somewhat expensive.

It seems like the solution to that would be to use multiple types of housing construction within the same city, and then people can choose one suitable to their situation. And to make other sensible choices like to put heavy appliances on the ground floor.

Yes. The comment you responded to earlier said "It wouldn’t be bad for one off where the lot was oddly shaped but to have that as a default for attached homes isn’t great."

And what I'm saying is the opposite. It's fine for it to be common as long as there are still enough single floor dwellings for the people who need them.

There should be all kinds of everything. A city should be a massively diverse cacophony of individual choices. That means that finding exactly what you want is going to exclude >90% of the properties -- but means that finding exactly what you want is going to be possible.

Like I mentioned, the layouts aren't great --unless-- it's one designed by a known architect then they can at least look nice from the outside, yet they are still constrained by the dimensions --which can be from 12-foot wide to about 20-foot, in most cases. Here[1] is a sample of stock that's about 30yo. in the background you can see the roofline of a newer design.

[1]https://imgur.com/a/pdHmByZ