Do yourself a big favor and check with the building/permits department of your appropriate municipality to find out what is allowed under the building code. Things not allowed and discoved can be ordered removed. No, this is not a communist plot; its all about basic safety.
If there are no restrictions, a good source for building specs are a number of books from Taunton Press. Alot of research has gone into what 'rise' a human is comfortable with and what 'run' is necessary to accomodate feet properly.