My stairs are 14" wide, and each step is 7" deep. There are only 3 steps. However, if I was to have them custom made (you lucky duck) I would make the whole thing wider, as when 2 try to use them at the same time, one will usually push the other off. lol.
Lo had a bad habit of jumping off couches and things before we got the stairs, and it took some time for her to remember that she was to use those instead of jumping. But now she doesn't jump off, and seems to like taking the "lazy way".
Finn doesn't know any different, I swear that boy doesn't think he is even capable of jumping. lol. (I'm very happy for that!)
Be sure to share pictures when they're all done!
Are you having them covered in carpet or do you have a plan yet?