George has the right answer. If the stair is a required exit we then only worry about the construction of the stair, access to the stair and if openings have to be protected. There is a great picture explanation sent out by the OFM that shows how to assess what openings need to be protected that I could email to anyone that wants it. If the stair doesn’t serve above the second storey, openings don’t have to be protected.
If the stair is not a required exit, it still has to be maintained and be safe to use. You would use Part 2 of the fire code for the maintenance of the stair.