The Stairmaster is modelled after real stairs, so you can definitely do your Stairmaster workout on your own staircase, or even stairs at the park.
You do have to consider the material that the stairs are made of, as real stairs have more impact on the joints than stair machines – which are also specifically designed to be gentler on joints. So make sure you still wear proper shoes and don’t forget to stretch your legs before and after.
Using a real staircase also means you’ll have to come down once you reach the top. This is good for interval training; but if you’re after a full-cardio workout, then you should stick with the Stairmaster as it only goes one way – up.
If you’re doing stair exercises as part of your rehab and you need to take frequent breaks, using the stairs is the better option as you can stop whenever you need to. With the Stairmaster, you’ll have to keep turning the machine off and then back on, and resetting it each time.