Slip a 1/8" x 1" wide peice of metal long enough to span the joists. Dig out the back side of the wallboard to allow you to place the metal up tight to the joists without bumping the wallboard out. Drill a hole at an angle to screw into the joist that barely shows, then drill and screw into the opposite joist. Line up your pancake box, drill and nut and bolt the box to the 1" metal plate.

I am exhausted. If there are joists up there, I can't find them. I have knocked with my knuckles - and then a hammer wrapped in a towel - for hours on end. Can't find them. I have run my stud finder with a piece of white paper under it over that rough ceiling until I can't do it any more. The light turns off. The light turns green. Run over the same area again and it doesn't do it. Run over it again and it does do it. Then it doesn't. The paper is only 8 1/2 x 11 so frustrating when you get to the edge of the paper. What a hunk of junk. I have hammered finishing nails through the drywall over and over again. Some resistance and then - slips right in. No joist. I've been standing on a 8' ladder working on a 12' rough ceiling for hours. I've got pencil, hammer, rag for over the hammer, stud finder, measuring tape, blue painters tape, drill and bit, extension cord, the hooks - all the tools - I'm giving up. This is apparently just not meant to be. Thanks for your time, everyone.

You can still move electrical boxes in a modular - I moved the one in the center of the kitchen before we had the house painted, it wasn't going to be anywhere close to the center of the (site-built) island. Also a recessed light that had "wandered" into the family room. But now that we've spent all this money just repainting (the modular factory fixed the cracks for free), DH does not want to tear apart the dining room ceiling and have to repaint all the way into the foyer. Plus, as he reminded me, I wanted the chandelier closer to the front wall because the table would be too close to the china cabinet if we centered it front-to-back in the room. The problem, as I discovered last night after digging through emails to the builder, was that they didn't place the sconces where I wanted them. Not a big deal, I'll move the sconce later if it looks really awful when we put the table in. Some of the cracks were really just bad tape jobs, edge of tape showing. Others were actual cracks factory said my builder should have taken care of before we painted. But my builder was very inexperienced (had just signed with this modular factory we wanted to use, they gave him our territory so we really had no choice). He was just throwing more mud on the cracks without retaping. Once they put the tape on, no more cracks (just some humps). Our old (1988) house had swirled plaster ceilings and skim-coated drywall, but I understand most stick-built houses these days are just sheetrock, flat painted ceilings anyway. We wanted to move in less than a year from when DH got new job, didn't think we'd make it if we stick-built. Plus a lot of my family has done modular, we thought it would be better quality since it was built in controlled conditions. And I couldn't keep an eye on a stick builder living 100 miles away with son still in school. Now, I just dry-mopped the dining room floor and we have a cracked board (splitting from end) 3ft from center. It'll be hidden under the rug. Either the end was split already, or it split when installer hammered it into the pattern (spiraling rectangles). Unless he can split it with a wood chisel, pull out the pieces, and just face-nail the replacement, we'd have to pull out the whole center of the floor (about 12 sf) to get to it. I have a lot of wood left over - should I ask installer to replace that piece?

@Webado, what are you on about? It isn’t necessary to cut a channel in the ceiling to run a wire. And those spray-on textured ceilings can be patched. Not a big deal at all. That’s just looking for something to be contentious about. Weird. Why do that? You also don‘t need to “break the wall” for wiring if the sconces (not ”scones,” which would not hang on a wall very well) are hung above a wall plug. And the chandelier height? Huh? There is a standard height for hanging a light over a table. That existing chandelier is hung way too high. If that were my condo, I would have the crew scrape off the ceiling texture, btw. The stuff breaks down over time, and it holds dirt. Again, not a complicated job (unless you‘re dealing with an older property and there is asbestos in the “popcorn” material), but it’s messy and takes potentially expensive hours of labor. The pro due is to spray the ceiling to soften the stuff, and then it’s scraped off, and finally the ceiling gets a skim coat of plaster. But I doubt this homeowner wants to get into any of that.