For climbing, "perfectly smooth" does not mean "smooth as mirrored glass". It does not require good dwarven stonework, magical construction, polish or sheetrock.
It simply means there is nothing to hold onto. A simple plaster and lathe ceiling, or stucco, or wood planks, gives nothing to hold onto and counts as "perfectly smooth" (unless there are big gaps between the planks). If you can't put your fingers and toes into cracks, crevices, crannies, holes, whatever, enough to get a grip, then it is "perfectly smooth".
Even a natural slab of rock could easily be "perfectly smooth" enough for this definition unless it has holes like swiss cheese or lots of cracks.
Most structures could conceivably hold his weight, but that doesn't necessarily mean there is something for him to cling to - he doesn't hang from the ceiling with suction cups or with magic; he needs to actually have something for each of his feet to grab onto.
Do you have a rules source that defines "perfectly smooth" this way? It is a big deal to increase the DC from 20-30 to infinite. Realistically, if the surface imperfections just need to be significant in size compared to the grabbing appendages. Real geckos can move on a typical "flat" ceiling. The bumps need to be larger for an 11' long version, but rafters or stone blocks would do. Also, the bigger the room, the less likely that the ceiling will be a single surface with no exposed beams.