Will it decay?

Will the ceiling decay?

No, it shouldn’t.

There is no foundation or pillar to support it…are you sure?

I’m pretty sure a door on a foundation will reset the decay timer for anything built on foundation(s) connected to it. There is a foundation below it, since there are stairs there, and you have doors, so it should be fine.

Edit:
Actually, that appears to be a ramp underneath it. But it is still connected to the foundation with the door on it.

Really? thanks