Today, I am going to run a thin bead of caulk underneath the separated seams in an attempt to 'glue them back down'. If this does not work, what are my other options? --68.63.xxx.xxx

Flexing of joists, moisture, improper mud behind tape when spackling, too thin drywall for the joist span, improper screwing, improper gluing. Could be Many different reasons. Fix with a spackle blade of mud put behind the tape. --24.152.xxx.xx

Roy, as NE said it can for a variety of reasons. Depending upon how fussy you want to be sometimes just using a decent flexible caulk like "Big Stretch" will make them less noticeable. If you end up having to refasten the seams & redo the taping, I suggest that you try using "FiberFuse" tape it works great on flat seams & is very forgiving for non professional tapers to use. Around here most of the lumber yards & big box stores carry it along with the regular paper tape & mesh tapes. --71.184.xxx.xx

The 8ft long cracks or openings here are about 1/16 inch. And it is an 8ft. ceiling too which creates a pain in the neck (literally). I am much better and faster with a tube of caulk as opposed to trying to re-mud a seam with a 6 inch drywall knife. After 25 rehabs, one DIY tool I have finally mastered is a caulking gun with cheap painter's grade caulk, which I buy by the case. --68.63.xxx.xxx

I love the Fiber Mesh tape with a sticky back. I used it yesterday to fix a hole made by a door knob. Is Mesh tape and your 'Fiber Fuse' product the same thing? How could anything be easier than sticky back mesh tape? --68.63.xxx.xxx

I have my guy caulk as you are doing. If the tape is really loose cut out the bad and caulk just before repaint. Way to hard in that 8ft seem to tape and re-apply. --63.64.xxx.xx

MYOB, I hate humidity.Your houses are from the 70s? as in 1970? many of mine are from the 70s also but i am referring to the 1870s --72.231.xxx.xxx

Ah yes Ken, 1870’s plaster and lathe. Mixed with horse hair. You’re not fixing that stuff with a bead of caulk! --24.152.xxx.xx

it holds the drywall up. --24.151.xxx.xx

I’ve seen that before RB. I’ve also seen regular yellow tape and paint. --24.152.xxx.xx

Band-Aid repairs wont last. I like RB's solution. A stained oak ceiling grid on 4' centers would solve current and future separation problems. And it would look amazing. --107.141.xx.xxx

Roy, if this is a house that you plan on keeping, put in the extra work to fix it correctly the first time. --76.178.xxx.xxx

On the plane you can fix with the grid well described, however if the corners are opening it indicates structural shifting which will require peeling of the sheetrock and examine to fix the flaws with the framing lumber, be sure of what you have before caulking. --76.188.xxx.xxx

Heat and humidity will do it - got a 3x2 garage the same way - best solution strip with some type of Lattice Molding. Go to a good trailer supply house they may have a solution. --72.173.xx.xxx

HORSE HAIR thats nasty-- but at least they used the whole animal!!!! --63.64.xxx.xx

MYOB lath and plaster a dying art.they installed lath boards then mixed up plaster and applied it,kind of a wet mixture literally with horse hair to bind it together. the lath boards are about 1/4 inch apart and the plaster would stick to it and get between the lath boards and stay there till it dried.I think 2-3 coats.When pieces of it break out we can sometimes replace with a piece of drywall and compound to feather it in but the easiest way is either remove it all or drywall right over it.The lath boards make great kindling,they will light with just a match,dont even need paper --72.231.xxx.xxx