Most buildings contain multiple uses - perhaps a residential tower sits atop a parking podium. Or, a commercial tower includes a retail ground floor.
The Stack order property controls how discrete geometries stack on top of each other. The higher the number, the higher it stacks in the building.
Only geometries on the same layer can stack!
Stacking Basics
Stack order is not the same as Levels. While levels determines the number of stories or floors in a building section, Stack order is relative to other geometries in the stack.
A geometry with 1 level can be stack order = 1.
A geometry on top of that may have 4 levels, but it is stack order = 2.
Adjust Stack
To adjust the stack order, edit its value in the properties palette on the left.
To add a geometry to the stack, Draw or move a geometry on top of another.
To adjust stacking behavior, select a force stack option.
Default - inherit Usage type stacking defaults
Always - stack if on the same layer
Never - never stack
By default, Building usage type geometries will stack if:
they are on the same Drawing Layer
AND
force stackis set to "default" or "always"
Stack Order is for building type usages! Roads, Paved areas, Basement, Generic Usages, etc do not stack.
Landscape usage type geometries will also stack on Building usages if the force stack property is set to "always." Use the force stack property to make landscape elements sit on top of building elements, to create rooftop gardens and green roofs.
Base Height
A Geometry can also inherit a base height, which controls how high the bottom of the geometry is from the ground plane.
When the base height of the lowest geometry in the stack order is changed, everything on top of that geometry will remain stacked.
When the base height of a geometry above the lowest item in the stack order is adjusted, the lower stack items are not affected.
Use Base Height to:
Simulate stacking between elements that are not affected by stack (such as generic geometries)
Simulate stacking on elements that are on different layers
For sky bridges / pedestrian crossovers between buildings