If you’re in the enviable position of being able to design your own staircase (which is absolutely fantastic in my opinion),… but you don’t necessarily know a lot about doing so. . . and this is ultimately something you’ll be living with for some time to come (as in near daily exposure to it).
I offer one point of possible warning. . . Be careful about designing something in the Abstract which you don’t have a Personal Feel for.
To make up an example of what I have in mind…
If space is tight then you might be inclined to use a tread size which has a 10" run on it… and it will probably pass code. and It will look great on paper because your saving some space. . . OR perhaps you’ll eventually discover that increasing the riser height will result in the need for fewer treads ( also a space saver). . . or perhaps the size of the landing will be reduced, or the width of the treads can be shaved down some. . . and on and on.
But, the problem that I’m trying to warn you about is this. . . Make sure you know what it’s like to walk that 10" tread before you commit yourself to having one simply because it was drawn out on paper, or brought into SketchUp via a plug-in, or was a posted model in the 3D warehouse. You may very well prefer a tread depth of 11" or more.
The combination of rise and run can make a major difference in terms of how comfortable you feel when walking the stairs. Narrow treads where your heal starts to overhang the tread nosing can flat out suck, and and Riser Heights can make a staircase unenjoyable to walk on when too tall.
And so far, I’ve only been talking about the comfort level here. There is also the utility side to consider where perhaps you’ll be carrying up some stuff rather frequently. In this case landing size and position can be a godsend when properly placed. . . Or depending upon traffic the tread width will determine if more than one person can be walking on them at the same time or not.
The building codes don’t necessarily protect you from bad design. which is what I’m trying do, and I hope you see the point I’m trying to make here.
And of course whether you use that or not, is entirely up to you. I’m just trying to make the case for personalized customization, which hopefully are a pleasure to walk upon once you’re done building them.