To figure out stair design, start as you did: calculate the vertical dimension between the top of the finish floor on the lower level to the top of the finish floor on the upper level. Thereafter, to design a stair for the given vertical dimension, you have some choices: 1) design to the code-mandated minimum dimensions; 2) design a stair much better suited to young and old who may be using the stair; 3) Or some other standard which fits your family's needs. Stairs are easily designed for virtually all framing commonly used in residential construction, whether solid joists, truss joists or whatever! It's not complicated. Do this make sense? Just keep in mind that the building code standards are the MINIMUM acceptable standards, and not always the most preferable standards for daily use.

Your architect will deal with that, among the numerous other code issues.

It appears that all of the joist sizes work with 16 risers. I prefer risers to be 7 1/2" and deeper joists are usually needed to avoid floor bounce. Cost of deeper joists is usually well worth it.

I don't understand your concern about the roof slope. The difference in slope is not likely to be perceptible nor is the roof likely to be that accurately built. The floor joists might even be 11 7/8 I-joists if the span is great.

The reason I am concerned about the roof slope is that the staircase will rise long with the ceiling, so that the vertical distance between the staircase slope line, and the associated rail, is constant. It would not look good for the staircase to rise at a lower rate.

The span will not be very long at all - at most about 14'.

Ideally i would love to hit the sweet spot of exactly 120" rise, as 16 7-1/2" x 10" (minimum run per code) steps, but short of cutting every wall stud (i.e., from the standard that results in a 9'-1-1/8" rough height), I'm not sure how to do it. For this, the equation must be:

120" = 109-1/8" + subfloor + joist

If the joist is 2 x 10" (9-1/4"), then it becomes

120" = 109-1/8" + 9-1/4" + subfloor

subfloor = 1-5/8"

I suppose I could simply put 3/4" & 7/8" plywood for a really thick subfloor? Sounds expensive!

There is one other thing I could do that would make sense. Presuming I go with a 7/8" subfloor, I would be 3/4" short. However, since the first 4 steps are to be winding, and thus would not be matched up to the ceiling - and as well, not in a straight line to begin with - and thus not something that could trip someone up any more than navigating the winding would. I could make those 4 risers each 3/16" less - which is allowable under code, as the variation can be as much as 3/8" for the riser - which would hence shave the 3/4", resulting in a net of 120". How does that sound?

This brings up a question about the run (@ 12" from the inner edge) for the winder steps. The code seems to only say that the run must be at least 10", and within 3/8" of each other - but doesn't seem to rule out the possibility that the winder run be within 3/8" of the straight-away run. In fact, the figures for the winders seem to show that the winder run is a lot bigger than the straight-away run.

Also about the winder, if I have a 4 step winder doing a net 90 degree turn, can the line along which the winder run is measured (i.e., the winder-line) be along the beginning & ending lines (i.e., that are at a 90 degree angle with each other) such that for 2 steps the winder-line is aligned with the beginning, and 2 for the ending? (The code seems to show this as permitted as well.) Or must the winder-line be normal (i.e., perpendicular) from the nosing for each step? The code does not seem to address this in text, but seems to give a lot of leeway in how this winder-line can be realized.

I worry about every detail but you are worrying about things I would not give much thought so it's hard to help you.

A 1" difference in rise over the length of a stair is neither noticeable or predictable.

Standard stud length should not be an issue; lumber yards should be willing to cut them to any length you want. Standards vary by town and contractor and shouldn't be a design issue.

You mentioned 5/8" subfloor; I use 3/4".

The new codes make winders pointless so I never use them. A square landing takes up little if any additional space and avoids difficult and costly handrail transitions.

Who will design and who will build this house?

This is being driven by your desire that the roof slope and the stair slope be the same. I've never heard of this before--seems pointless to me. Are you sure that anyone will ever be in a position to see the roof slope and the stair slope together at the same time from anywhere inside your house? And if they do, will they expect the slope to be the same for each? A very unusual situation! I'd be more concerned with the design of the stair and it's aesthetics and comfortable functioning. For example, will the stringer be exposed and free-standing, or will it (and the space beneath) be enclosed with gypboard? Will the risers be open or closed? How will the handrail be designed--will it be free-floating above the stair, will you extend gypsum board above the stair and attach the railing to it? So many design issues to resolve with a stair beyond the rise and run ratio. Good luck!

If you're concerned about it matching, wouldn't it be easier to fur down the ceiling to match the stair slope?

I am designing the house with as much detail as I think is necessary, with the architect having a very easy time to make a stamped drawing out of. Any detail I leave out could result in something that is not what I want. I understand that there is some play in the measurements, but I figure that I ought to at least get the design specification perfect. I will get a contractor to build it.

As for the ceiling matching the staircase, I actually had that in my old house - a 10/12 slope, under obviously a looser code! (It had a 2 step winder @ 45 degrees, where the inner width was definitely less than 6".) It looked very nice, and is great cheap, dramatic way to have a staircase - and I couldn't fathom having the slopes be different.

As for the code now being such that a winder doesn't make as much sense, I agree to some extent. I could easily change a 4-step winder into a 3-step set having the middle one as a lander, but at the cost of a run segment. I had done some preliminary analysis, and it seemed that I needed that extra run to be subsumed by the winder, and the situation in which there were 2 steps before the lander being too much out of the staircase. Of course, when I get down to a final design, I'll be able to determine if I could get by with a lander. I had been looking at an 8/12 roof & staircase, but as I have changed that to a 9/12 - and an extension of some other dimension may allow for 2 steps in front of the lander - this problem may already have been obviated. Of course a winder does have some aesthetic appeal, but maybe at a relatively high cost and safety issue.

Now, as for a staircase with a lander and 2 steps in front, would there need to be a guardrail? It seems that the code says that only if a section has a total of 4 risers does there need to be a guardrail - and since this would be a total of only 3 risers, a guardrail would not be needed. This would be nice as the staircase is to not have a fence, but rather have a solid wall (i.e., at 3' or whatever above the run line) with trim on top. The guardrail could be hidden on the inside of this wall.

Now that I think about it, I really should do as much as I can to get by with a lander and 1-2 steps in front. It really would make everything easier. I could still extract the 3/4" on the 2-3 initial risers with no problem (i.e., as less 3/8" or 1/4").

If the 2012 IRC applies, a stair has two requirements: one for a Guard and one for a Handrail. In many cases they can be served by the same element. A guard is required on the open side of a stair where the tread is more than 30 inches above the finish floor. It must be at least 34 inches above a line connecting the leading edges of the stair treads.

A Handrail is required on one side of a continuous run of a stairway with four or more risers. The height must be at least 34" but not more than 38" above the line mentioned above. Handrails for stairways shall be continuous for the full length of the flight, from a point directly above the top riser of the flight to a point directly above the lowest riser of the flight. Handrail ends shall be returned or shall terminate in newel posts or safety terminals.

A Guard can also serve as a handrail if it is 34 to 38 inches above the line mentioned above.

Making the risers different heights is unwise. The difference is far too small to be noticed or appreciated and will be a major headache for the fabricator. Stairs are not built to individual riser heights; the fabricator is given the number of risers and he distributes them equally between the floor levels whatever that might be. He will not take the floor to floor height on the drawings seriously. Your approach will create confusion and possibly cause a costly mistake.

"with the architect having a very easy time to make a stamped drawing out of."

I'll take that bet in the negative for $100.

By law, architects may only stamp drawings made personally or under their direct supervision, assuming in your jurisdiction construction documents for a single family residence require an architect's stamp.

Obviously, the architect would be making his own drawing, but it should match what I give him, in as much as it is "designable". I can see how some of my requirements cannot really be put down on the drawing, and that depending on the design dimensions when the actual dimensions would probably be different is not proper.

It seems that the only design concept that must be discarded here is the height of each riser; the risers must simply be 1/16 of whatever the ACTUAL height ends up being (which would be 9'-11-1/4" if using 10" joists, and the carpenters were perfect). I still want the wall in front of the staircase to go up along the slope of the roof, so it looks I need to specify how high to make it based on what that height ends up being.