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.

That is *WAYYYY* too thick! On butt joints at least.

Step #1 is to make sure the joints are securely fastened. If they aren't,
the joints will crack. One way to tell is to put your finger lightly on the
joint and have someone else thump the wall lightly with their fist a foot or
so away. Can you feel movement with your finger? (Note: you can't do your
own thumping).

Step #2 is to bed paper tape. Use only enough mud and width to bed and
slightly cover the tape.

Step #3 - after #2 is dry - is to sand as needed and apply more mud using a
wider knife. You aren't trying to cover the tape with this, you are filling
the gap along the edges of the tape created by the taped area being thicker.

Step #4 is to repeat #3 but with a still wider knife. By the time you work
up to a 10" knife the tape hump will be pretty much invisible even if it was
on butts, not tapered edges.

You mentioned that the cracks were over 3 mils. A human hair is about 3
mils so your cracks don't sound like a disaster. If the sheets are well
fastened, rubbing some acrylic caulk into them before painting as Norminn
suggested (she's a sharp cookie will fix them nicely.

--

dadiOH
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