Truss uplift

 
Truss uplift or truss lift is when the wood in wooden trusses shrinks, or cures, and the bottom most piece bows upwards, most notably near the middle. Truss lift is an issue in wood frame construction where non-load bearing drywall walls meet drywall ceilings, as the truss lifts it pulls the ceiling drywall up. This in turn pulls the angle tape out of the corner and can damage the spray texture. One solution is to not fasten the ceiling drywall within two feet of a non load bearing wall, and rather use the drywall on the wall as support. This technique will allow the ceiling board to bow down and stay tight to the angle over time as the truss lifts.