To Create an Interference Condition in a Slab

Use this procedure to create a stair interference area in a slab. When you add an interference condition between a stair and a slab, a box is cut out around the stair based on the specified headroom height and left and right side clearances for straight and multi-landing stairs or inside and outside clearances for spiral and U-shaped stairs.

Specifying the left and right side clearances for a slab interference condition

Specifying the inside and outside clearances for a slab interference condition

1. Create a stair that intersects with a slab.
2. Double-click the stair to open the Properties palette.
3. Click the Design tab, expand Advanced, and expand Interference.
   

4. Set the size of the interference condition:

   If you want to…	Then…
   specify the height above the treads for the interference condition	enter a value for Headroom height.
   specify the left and right side clearances for the interference condition for straight and multi-landing stairs	enter values for Left and Right Clearance.
   specify the inside and outside clearances for the interference condition for spiral and U-shaped stairs	enter values for Inside and Outside Clearance.

5. Click in the drawing, not on the stair, to remove the selection.
6. Select the slab to intersect, and click Slab tabModify panelInterference Condition drop-downAdd.
7. Select the stair, and press Enter.
8. Select the shrinkwrap effect, and press Enter.
   

   Creating a slab and stair interference condition

   Note: Changing the Interference values of the stair changes the size of the intersection with the slab.