Ceiling in bay window is cracking, looks like right along the bead on the header outside corner (I think that's what to call it). I chipped off a bit along that line and it looks like they didn't tape over the bead, but there also seems to be some give in the ceiling drywall, like it's not fastened to the joists really well. I searched for nails/screws, and can only find what I've marked with red in the last picture. So from that, I think I can tell where the joists would be - I've done lots of knocking, but am having a hard time hearing any difference in sound. I know I can put a small nail through to confirm, but thought it wouldn't hurt to ask here before I go putting holes all over the place. Can I be pretty sure that where I've marked in blue in the last picture is where the joists are? Any others that are typically in a bay window? Feel free to draw in.

 

There is no way to know. You would usually use a studfinder for that.

Regardless, I would be ripping that old corner off and replace it with a new metal reinforced paper tape corner.

 

Thanks for the idea of paper faced bead. Was originally just thinking to tape over the existing bead, but now I may just do what you suggest.

 

Yeah, you don't just want to tape over something that is no longer secured. You have to remove anything that is loose.