The gaps is no gh Problem. It’s because of the high Surface curvature. Just higher the Domain start of till they arent visible anymore.
For the halfs on the edges, I tried to rebuild your Surface as near as possible but “bigger” (not scaling it) Used @laurent_delrieu’s script for that.
VoxelOnSurface_re_re.gh (77.8 KB)
Btw: I wouldn’t mix a stepped Roof with a underlaying waffle structure. And yesterday you told me how important it is, the waffle can’t be simply extruded, because for your Renderings they can’t hang out of the Roof. How should that be possible with that fat boxes on the Roof?