Staircase Design. Why is the first riser smaller than the rest?

[samuelzergling]

Every automatic stair, or stair by sketch, is ~1/4" smaller than the rest of the risers. This is not a setting that can be controlled from the standard Revit 2024 LT stair tools. This is not ok. In the US, we are only allowed 3/8" variation in stair riser heights. This is an issue because when you add in the finish floor, which gets installed after stairs, you end up with a riser height for the first run that is not code compliant. 

Would love an answer on controlling this. 

[barthbradley]

So, sounds you are measuring the stair's first riser height from the Finished Floor which is 1/4" above the stair's "Base Level".  Changing the stair's "Base Offset" to "1/4"" will correct the stair in the model.  How it's done in the field is for you to decide.  

https://help.autodesk.com/view/RVT/2022/ENU/?guid=GUID-541EB756-8376-4522-BFA1-141C22346ED8

[samuelzergling]

Yes @barthbradley I did this as a work around. I set the height to the same height as the flooring to be installed. This allows the finish result to be acceptable by code, but Revit is still having the first riser be different than the rest. You would think there could be a manual override to input the height. 

Do we know why Revit makes the first riser different than the rest, and at a seemingly unknown measurement. Is it attempting to average the majority of the stairs to a 1/8" or other whole increment? 

Kind regards,

Samuel 

[barthbradley]

Very mysterious. Riser heights should be consistent. In fact, Revit cannot do what you claim it's doing on your end, which is making the first riser height different from the rest.  

Post your Revit File and let us see it to believe it.  

[barthbradley]

How are you determining the first riser height? Are you pulling a dimension?  If so, maybe the problem is with the dimensioner  or with the Dimension Type.  Maybe this has something to do with Rounding.  Change to 1/256" and see if the risers all measure the same as the Actual Riser Height shown in the Stair's Instance Properties. 

[samuelzergling]

Please find attached rvt file. 

Here is a screenshot of the measurements. Revit doesn't consider the first riser the same way it considers the others because of the tread. So it's actual riser height is different for the first riser, which deserves a manual override based on the architects choice for the assembly method. I love revit, I'm sure I'm about to learn how to do this properly.. but as it it seems odd I can't make the risers literally the same size. 

[barthbradley]

I don't see any issues here with Revit.