Spiral Staircases!

I do not think anyone loves it in the size typical of nyc. Spiral staircases are mostly used due to space constraint. Of course, you can have 15 ft diameter spiral and it can be a piece of beauty. Most are much narrower.

"Oh, great ... It has a spiral staircase" said no one.

Spiral staircases are really beautiful, yet not practical at all. I've never had such experience, but a good friend of mine once lived in such apartment. I asked him to write you back.

This is the only spiral staircase that I've seen that I did not hate:
https://streeteasy.com/building/521-west-47-street-new_york/phb

I've heard that spiral staircases decrease marketability and resale value - is this true? Or is it just a reflection on duplexes being less valuable than one floor units of a comparable size?

Just trying using one while carrying a baby or after having a few drinks. You will have your answer.

"is it just a reflection on duplexes being less valuable than one floor units of a comparable size?"

teijoluis, I think it's both but spirals are a fact of life in many NYC apts. Sometimes, there are no alternatives.

http://openspacesfengshui.com/feng-shui-tips/2012/07/feng-shui-safety-spiral-staircases/

In my former CT weekend home, we had what we called "ship stairs" similar to this photo but more attractive with a landing in between the first and second floors.

http://blueseanotary.com/ships-ladder-plans/ships-ladder-plans-wood-ships-ladder-wood-ships-ladder-cool-ladder-idea-simple-ship-ladder-takes-up-less-room-ship-ladder-building-code/

At first we thought they were rustic, craftmanish and fun but later realized that they were a little dangerous and not very accommodating to small children, the elderly or pets. So, I considered replacements such as a traditional staircase or a spiral. I was told by various general contractors that there was not adequate floor area to build a traditional staircase and decided that a spiral staircase was possibly even worse so we decided to keep it the way it was.

But when we put the house on the market a couple of years ago, we found that the stairs were a big negative. So I called in a stair builder who figured out how to make it work with only a small variance required for the width of the stairs. Once completed, it completely changed the feel of the house and we sold it a few months later.

To me, the moral of this story is that when making investment decisions, try to base them on not just on what think but also on what the next buyer will think.

Re: a little dangerous,
I see so many staircases with one side open and wonder how they passed inspection (and how no one's died from a drunken slip). I thought that wasn't legal? Anyone know for sure what current code says?

30, not sure about legality of an open staircase. I only know the local building official said our staircase was "grandfathered" therefore legal. But if I ever rented the house out (which I considered at one time), I would certainly have worried about my liability in the event of a "drunken slip" or other mishap. Not just the open side which is dangerous enough but also the odd staggered treads which in complete darkness felt normal to climb but when seeing it in broad daylight, a little scary and disorienting. But we rather quickly got used to them and we ran up and down with abandon.