On Jan 6, 8:37*am, Robert Macy wrote:
how to repaire [and prevent future cracking] WITHOUT adding a big LUMP
to the seam?

The wall run is around 60 feet and 10 feet tall. the junction right in
the middle is wanting to crack. Trying to keep from forming lumps on
the wall, I cut down, used paper tape with a layer of mud under and a
layer on top. [Many may remember the problems I had posted earlier. I
tried to wet the tape first thinking of wall paper and how that
shrinks to fit, but wetting CAUSED the paper to 'slide' as it dried
and thus a crack, so in response I took all that out and did it again
with dry paper tape, which did work better. Only had the tiniest of
hairline crack form all summer long only about four feet of run on the
wall only.]

Well this winter as we isolated that section of the house - meaning
cooler temperatures and probably contracting drywall sheets, the
crack(s) opened up with a vengence! I mean over 3 mil separation!, but
worse the crack is the full floor to ceiling AND even now goes up
along a ceiling section which I never had trouble with before. I
suspect in the heat of the summer the crack will close back up, too.

Yes, I know houses change shape with time, but this seems too much to
be caused by 'settling'. My conjecture is is that this is more caused
by 'flexing'. Oh yeah, the seams are ON a stud(s), so there should be
no reason for movement there.

So, my question is
How do you repair/prevent cracking at drywall seams WITHOUT creating a
huge lump on the surface? I already have built up 1/8 inch thick to ++
on these stupid seams.

You mean the wall is 60 feet long and 10 feet high, and there is a
vertical crack somewhere toward the middle of the 60 feet??? That
long a solid wall, without any expansion provisions is asking for
cracking if it experiences a full range of temperatures and humidity.
Is this an interior wall, surrounded by interior spaces on all four
sides, front and back and two ends, or is one side or one end an
exterior facing wall? What do you mean by isolated, isolated from
what???

A better description of the entire situation would allow folks to give
you a more meaningful and workable solution.