Replacing Existing Stairways
If you're going to
replace an existing stairway that's damaged or make any repairs, start
by contacting your local Building and Safety Department to find out if
there are or are not any building code requirements that will be
mandatory for you to follow.
There are exceptions within most building code books for replacing existing stairways. Some of these building codes might allow you to keep your current tread and riser sizes, if they are going to create major problems for the structure of the building.
Special Tip: If you're planning on replacing your existing stairway and you can bring the stairway system up to local building codes, I strongly suggest that you do. Remember, most of these building codes create safer places for us to live.