Add a winder stair to the model and use grips to make adjustments. Change the point where the winder starts on the stair run in the Properties Palette.
This video demonstrates the following:
With the Stair tool, you can add an L-shape or U-shape winder stair to your Revit model.
In this example, an L-shape winder stair will be created. Based on the properties of this stair type, Revit automatically calculates the tread depth and space requirements to reach the next floor.
Before placing the run, you may want to modify its instance properties to change parameters such as the Winder Style or, in this case, the Actual Run Width.
To orient the preview as needed in the drawing area, you can rotate it in 90-degree increments by pressing the Spacebar. If you just need to flip the preview along its default placement axis, select the Mirror Preview option on the Options Bar.
Move the cursor to position the stair so that it aligns with the adjacent wall, and then click to place the stair.
If you drag the arrow control at the run end, the start and end positions of the run change, and the steps of the winder legs rebalance automatically.
You can also use the Properties palette to replace winder steps with parallel treads at the lower end and the upper end of the winder run.
Click Finish to complete the stair. The default railing is automatically created with the finished winder stair.