If you are in the process of designing and installing a new timber staircase for your home, then the following will be useful to you in measuring the stair opening accurately. This is very important and will affect the final design that you go for.
The first thing that you need to do is to measure the floor-to-floor height, not forgetting to include the thickness of the upstairs floorboard.
After you have done this, then it is now time to measure the stair opening from the back wall to the trimmer joist, in order that the staircase design allows space for the plaster board.
The next step is to get help with designing your actual staircase. There are now companies that can assist you through every step of the way as you go from start to finish. The chosen staircase should suit your requirements but fit within the measurements taken above.
This is why it is always necessary to allow for adjustments as well as plaster and fitting tolerance. So always be sure to get accurate sizes when measuring the space. And so hopefully you will be left with a perfect design that is certainly achievable and you can then get to work on the installation of the wooden staircase itself.