Hello Duayne,

To make the stair rule comply to a specific tread width :

Set the Units to a precision of 2 decimal places.

In the “Stair Well Parameters” dialogue box use the “Control” button to set the minimum tread width to 10.5 and the max to 10.501.

To make the stair fit the new parameters click the “Help”  button and in the list choose the best new config : 

When you exit the “Help” box the “Stairwell Parameters” OK button should be green and the treads set to 10.5.

All the best,

Ness

Hi David,

You are right the general stair rule as defined by the French 17th century architect Nicolas-François Blondel, as 2x rise (height from step to step) + 1x going or width of step should be more than 60cm and less than 64cm. Not sure where you found the formula with the “h” for the step width though. 

This rule can be bent a bit but is surprising efficient in producing a comfortable stair. 

One  has also to take into account maximum and minimum step heights and widths.

20cm is usually considered a maximum height but I can go up to 21cm if necessary. These values can be set up as you want in StairDesigner control values.

I’ve set my StairDesigner control values as in the picture and still have to bend them sometimes when a stair is a tight fit:

The important thing being to get as close as possible to rule while maintaining a maximum tread width.

All the best,

Ness