There are many different ways to look at a stairway:
Layout- A draftsman laid out with a couple of lines on a print saying where the stairway goes.
First lets look, does it fix in the opening from the finish floor 2nd floor to the finished floor on main floor (using an 8’ wall 9 1/2” joists carpet on 2nd and 3/4” wood on main floor sets the actual height of the stairs the code requires the tread height not more than 1/4” different in all the treads) the stair rise max. height set by the code is 7 1/2”.
Did the draft’s man draw in 15 rises, and 14 treads. The rise works out to 7.17 or 7 5/32” now lets see if the stairway hole is long enough, The code requires the tread to be 10”that make the rough opening 11’0” this size will just make the minimum head room height on the stairs.
Next let’s look on the print how wide is the stairway from wall to wall (the width) the code requires a 3’0” clear opening. This means you must frame the walls at least 3’1 1/4” for sheet rock and taping compound.
If the handrail is not removable than you must add the space from the wall to the rail plus the rail to the framed opening.
If the stair way has 1 or more landings or turns it’s in your best interest to make the stairway 8”wider to bring furniture and bed frames and mattresses up and down the stairs.
Another area you have to watch for is if there is a wood or stone nosing even carpet wrap under the balusters on the sides of the stairway if its on the side of the fixed hand rail you can ignore it.
If it’s on the other side of the stairway you must frame the walls wide to account for the 3’ clearance.
Why the 3’ clearance 1 haling in refrigerators, laundry equipment need the room as well an ambulance stretcher in case of an emergency.
Framing- When framing a stairway the landing at the bottom of the stairway as well as any 90°angle platform on the run of stairs must be at least as long as it the stairway is wide this is code.
Many times I have come to houses 1 and 2 years old and going down stairs to the basement and land IE concrete floor from the stairway to the concrete wall dead ahead was 30” or less this is not legal.
If the stairway from Sheetrock to Sheetrock measures 36” then that is what is required at the bottom of the stairway to the wall.
Next the code no longer allows the builder to hang the stair jacks on plywood they now have to be installed with metal hangers (like a joist hanger).
Using poor quality wood like spruce, pine or fir will in time create squeaks in steps; using a plywood beam like a micro-lam will stop these squeaks.