We are in the design phase of a Tuscan style house

Who is doing the design?

We hope to be able to have a small apartment inside the tower

Then the apartment size will influence the dimensions, don't you think?

we cannot go higher than 35 feet

You could fit 3 floors in 35 feet. Does the designer understand construction?

Why do you want a 35' tower? Are you able to visualize this height?

I'm asking what the width should be for a tower that is 35 feet tall

Depends on what the tower looks like, what is inside it, and what's around it.

Gosh I don't know maybe 20' there is no way to answer this question you need an architect and they should advise . I have no idea what an apartment will look llike in a tower entry .

The tower also has to be in proportion to the rest of the house. So, maybe not this. (Although in general, I really like David Adler’s designs)

But, the tower does contain a couple of bedroom-sitting room-ensuites and a ”den”:

A ”tower” by definition is narrow. With the limitation of 30’, you are talking maybe a 15’ square room, with a big chunk of that taken away for stairs on both floors. You perhaps can fit a small bedroom on the top floor, but in no way will it be large enough for an apartment. If youbexpend the width, it will no longer be a tower. It will be just another addition jog.

How large is a "small apartment"? Typically studio apartments in the U.S. may range from 200-500 SF, or larger. Scissor stairs will add another approx 128 SF or so. If my quick calcs are close, you are looking at a tower that is approximately 328-628 SF or so, depending on studio size. You can't minimize the stairs by much and still meet code. That's a comparatively large tower I think...how large will the rest of your house be?

Thanks for all the comments everyone! I did not get notified by Houzz that there were replies, so I just happened to see them now. Although a couple of you nailed it, some were confused by my question as I failed to be specific. …I was asking about proportion and what dimensions would work so that the tower is wide enough to hold, albeit a “tiny” apartment, but narrow enough to still look like a tower (as opposed to a box). I have come to the simple conclusion that the proper ratio is the height should equal at least two times the width. However, in order to make this apartment as comfortable as possible, I am pushing the width to 19 feet wide. …With the 35 ft height dictated by county code, I’m hoping this will still work visually.

Why do I want a 35' tower?? Because that's the height restriction for the county, and we have a gorgeous view, and it’s a Tuscan style house—and why not? ;D

—And yes, those of you who mentioned stairs are exactly right. I also failed to mention that the stairs will be on the outside of the tower, so as not to take away the square footage of the interior space.

I have attempted to work with several architects, but I always seem to want to do my own thing as opposed to what they want to do so I keep taking it back. Once I get the design where I want it, obviously, I will turn it over to an architect/draftsman.

"the stairs will be on the outside of the tower, so as not to take away the square footage of the interior space."

Whether the stair is on the inside or outside of the tower, they still take up square footage and volume. Do any of the architects seem upset that you "always seem to want to do my own thing as opposed to what they want to do so I keep taking it back"? Make sure your house does not impede on anyone else's "gorgeous view".

You want a resident to go out in the rain and snow to go upstairs to bed? That is not how that works. That is not how any of that works. You need to rethink this. A lot. You WILL be subject to building codes on this, as well as local environmental regulations. No point planning this in a vacuum without an architect's knowledge of those limitations.

@Mark Bischak, Architect... I'm not following how the outside stairs take up interior space, but thank you for your comment. We are fortunate to have a large 2+ acre lot with open land all around. The property is on the side of a steep hill with over 10 acres behind us where there is no buildable space so the tower will never block anyone else's view. As far as architects being upset, I think it's more of an ego thing as they want to be in charge and they believe their ideas are superior. As for me, it is my house and I'm putting a ton of time and money into building it and I'm the one that has to live with it, so I want what I want. If an architect gets upset in the process of me getting what I want when it's my time and money that is being expended, that sounds like their problem. ;-D

@DeWayne... Thank you for your concern. I used the word "apartment" to describe the unit to clarify that it is a self-contained unit with albeit, small bedroom, bath, kitchen/dining/living area even with a stackable washer/dryer. Here in California, no one gets away with building out of code, so that's not going to happen here.

Who will use the apartment and go outside in the rain and cold to enter and leave the apartment?

Even if the stairs are exterior they will still require interior space for access at top and bottom of the stairs.

This is really not a very good idea. Time to move on...?

You have to go outside to enter and leave any home, right?

I would research the Golden Ratio. I believe it is 1.678. That gives you a pleasing vision. That would be 20.858. But that does not seem very "tower-y"

Blue, of course one has to leave the outside when entering a house, and go outside when exiting...for most houses!

What one doesn’t have to do is go outside when one is already in the house to go to another part of the house.

Maybe this is an apartment for a different dweller?

Look at it as an entirely separate, self-contained residence. Yes, they will have to go outside to go to work, shopping, etc. Just like the rest of us.

Yes, of course. That’s why I specifically stated that the stairs will be on the outside of the tower, so as not to take away the square footage of the interior space. :)

HU has a good point.

If the stair is on the inside, it takes up square footage. If the stair is on the outside, it takes up square footage. The stair does not disappear if it is on the outside. A stair on the inside will cost about the same as a stair on the outside. Both will have the same number of treads and the same number of risers, and both will require a handrail(s).

If you will note, the whole foundation and design takes up the same exact space, whether the stairs were located inside the box or not. The whole requires the same landings, rise and run, and occupy the same volume. Locating the stairs exterior to the building envelope does not buy you any additional space inside the envelope. The usable interior space remains the same. It does complicate the support requirements, and lends a certain industrial/penal lookout/forest service vibe to locate them exterior.

Sounds like a very odd and impractical concept to me. Is this tiny apartment to be used for rental income? To house an adult friend/family member that won’t live in the main house? To serve as a temporary Away Space for a resident of the main house?

Regardless of who lives there, they would presumably be willing to (for example) cook and eat on floor #1, go outside up the steps to relax in a living room on floor #2, and later go outside up more steps to bed on floor #3? Then, after they’re in bed, curse because they can’t remember if they turned off the oven.