Do pads ignore phases? - getting overlap error

[3dway]

We're doing a reno and the former garage will become basement space.

I have a topo surface and a pad in the garage. I demolished it in a demolition phase that I made. When I try to create a new pad in the new construction phase, it tells me that pads can't overlap, while I'm certain that the new basement slab does not overlap any other pads in the new construction phase. I only have one other slab in the new construction phase and they share an edge. To be sure I even pulled the new slab edge off of the existing one so that it's impossible for them to be coincident. The only other slab that it could overlap with was set to demolish one phase earlier, so I assume it's the one causing me greif.

can I modify the height of a slab over phases? 3dsmax keyframe animation comes to mind. I can only think to drop the pad in the garage to be the new basement slab when we're looking at the new construction phase. I don't think it really works this way. From what I can tell, phases are more or less fancy visibility settings.

[3dway]

A bit of a bump for myself here. Some of what I've read on pads says, just cut a hole for the house and use a floor for the slab. May do that.

I also had trouble with the topo surface at a window well. The "earth" would show up in the foundation wall between the basement space and the window well.