troubleshoot crown mldg

anyone ever seen crown molding seperate from the ceiling?
it's all throughout the house, every room
1/4 - 3/8" long gaps... the ceiling looks very flat
the gaps are at the top of the mldg, it seperates from the ceiling, you see the caulking pulling here and there...the caulk does not stretch...
so it needs a caulk job, but I cannot imagine what is causing this
during the summer there are no cracks during the winter it looks awful
my guess is that the house shrinks during the winter even the house has settle on one side leaving small stress crack in an interior wall...
but this shrink swell winter summer mlding pulling loose
i have never seen this
it's all painted see...
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My first guess would be that you have trusses rather than a cut roof. Trusses are much more prone to this seasonal uplift. Only you can decide what is the best cure. Latex painter's type caulk is not good at stretching. There are caulks that are much better about stretching, though you must be careful to avoid bonding to anything more than 2 surfaces by using backer rod.
Here is some interesting reading on the problem: <http://www.google.com/search?hl=en&q=truss+uplift&btnG=Google+Search >
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If your house has truss rafters, that might be the problem. A condition referred to as truss uplift can cause the ceiling to rise, especially toward the center of the truss. It occurs mostly during the winter. Since the bottom chord of the truss is usually embedded in a thick layer of insulation, the heat from the house keeps it dry and it tends to shrink. The top chords of the truss are in higher humidity and expand. This differential moisture will cause the bottom chord of the truss to rise and, consequently, the ceiling will rise. Since the crown molding is generally fastened to the top plate of the wall, it stays down and a gap forms. At times the ceiling will crack during the winter because of truss lift, then the cracks tend to close during the summer. You can probably tell if this is the cause by noting how the trusses run and observing if the phenomenon is worse toward the center of the truss.
The only solution I know of is to fasten the crown molding to the ceiling rather than the wall so that it can rise with the ceiling. If you add caulk when the gap is present, the caulk will have no place to go when the ceiling comes back down.

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HarryS wrote:

Thank you
this makes alot of sense,
i've never heard of this
evidently his builder did not know about this... I read there is a solution to this, an L bracket
it is probably too late to install L brackets, or a pain in the buttox
we said the same thing, if we put caulk in now...where will it go when it shrinks... it's going to push on the molding..but I doubt it would be very visible..
I don't know, maybe a few L brakets in the attic could minimize the seasonal seperations
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