I need to replace a couple of drywall sheets on the ceiling. The ceiling has already been taped and painted, so now I don't know how I can nicely re-tape and re-mud seams between the old sheets and the new one. As seen on the photos attached, old sheets have crumbs and leftovers of the old tape, so if I put new tape over old sheet there will be bulges etc. How can I get around this? What can normally be done in such situations?
The best way to install the new sheets is to first remove any dried compound from the edge of the existing drywall that would interfere with the new sheet butting against the edge.
Once the new sheet is secured cut away any ripped or torn paper. Also cut and remove any loose or cracked sections of drywall.
It doesn't have to look pristine. You just want to be sure there's nothing to hinder the compound from adhering (like loose pieces) and small chunks will prevent a smooth finish.
Lastly, apply compound to joints as normal, tape, press, apply 1st coat, let dry, apply wider 2nd coat, etc.,etc..