I do not know as a certainty. I do know that if one builds a hut with a floor resting on the ground and that floor covers a spawn point for sticks, one will have sticks spawning on that floor. The presence of base structures, fires, workbenches, standing torches, and the like does not prevent such spawning.

Creatures may or may not spawn on a floor placed on the ground. I do not know. They will not spawn in a radius of base structures.

For the paranoid, standing torches inhibit creature spawns whether lit or not. Placing one or two in the rafters should preclude creature spawning on a roof.

Snarks will spawn anywhere.