Hi Serge,

Can you post your stair-file to have a look at. However, the thread width in stairdesigner is calculated from the step-nose of the first step until the step-nose of the last step divided by the number of steps which is the correct way to calculate. When you add nose space it will enlarge the steps but will not change the tread width as the distance between the step-noses is not changing. This can only change when the flight is extended or shortened.

Here is a little drawing showing the different aspects of the stair values.

regards

Michel