I thought I would repeat a thread I posted just minutes ago titled, ‘Classic truss uplift.’
Truss uplift phenomenon, is common among homes built with roof trusses as opposed to rafters, and should be narrated as such.
When a house suffers from truss uplift, the top floor ceilings assembly literally lifts, rises, off interior walls in the winter, and settles again when warmer conditions prevail.
At first glance, during a home inspection, one may hypothesize, the floors have settled. Actually the ceiling has risen sometimes creating ‘a gap’ at the ceiling, wall intersection, as much as (2") two inches at times, where an ‘interior wall’ meets the ceilings.
In this case, lift above a doorway, in a wall in the center of the second floor of a house. As well, this particular home had very wide eaves. Over 36" inches, or 3’ foot eaves overhangs on all sides.
Cause of Truss Uplift. Attics of newer homes have lots of insulation and ventilation, as in the case of this 1985 home that added 8" inch dense glass fiber batt insulation burying the bottom cord beneath the insulation allowing the chord to remain warm and dry.
The top chords, on the other hand, are above the insulation, exposed to cold winter environments in a well ventilated attic.
Cold winter air, as we have experienced, combined with very high relative humidity, as exists in Southern Quebec, Montreal, Canada, allows an upper chords to absorb moisture from the air, causing them to elongate, creating a bow at the bottom of the chord, enabling classic truss uplift.
Recommendation. Redecorating the ceiling wall intersection is an easy fix. Molding attached to the wall only.