How Do You Stop A Truss Uplift?
Truss uplift is caused by wood's natural response to moisture exposure. This response occurs when humidity changes differentially in two areas (an attic floor and attic ceiling, for example). A truss's top chords expand as their moisture content increases
Whatever the reason, the problem is real, but truss uplift is not a structural problem. This movement — which can just cause a simple hairline crack at best or, at worst, create large gaps and cracks along the corners — is a cosmetic problem, mostly in homes in cold climates
The space in between is the attic, and most homeowners insulate this space by spreading material on the lower chords of the trusses. ... If the trusses are nailed to the wall plates, the resulting distention at the points where the upper and lower chords meet can separate the ceiling from the walls