jim wrote:
Son - in - law (ex to be) decided to do this old guy a favor and
drywall the cottage mud room. Left the plastering / mud to be. Only
problem is that in several joins he did NOT butt the tapered edges
together. Thus there is no "groove" in which to fill with mud and
feather out for the smooth finish. Any way to remediate this other
than rip it out?


????? Taper to butt? Butt to butt? Impossible to not have any taper
to taper joints unless they were cut off completely. Not likely. You
may have a gap between tapers and that is okay if it is not too big.
Actually that gives you a stronger joint with a small (1/8") gap between
boards.

Butt to butt joints are also fairly easy. Put a small strip of mud on
each side of the joint first. After that dries, then do the joint and
level it out. SOP.

Mike D.