Why Your Ceiling Cracks Where It Meets the Wall

The short answer

A straight crack that runs along the line where the ceiling meets an interior wall, opens in winter and closes again in summer, is usually truss uplift. It is not usually a foundation problem. The roof trusses above the ceiling bow upward a little when the attic turns cold and dry, and they lift the ceiling drywall away from the top of the wall below. When the weather warms up, the trusses relax and the gap closes. The fix is to let the ceiling move without tearing the joint, not to keep re-taping it.

Why it happens

Most homes built in the last few decades, including the production homes across San Antonio's newer subdivisions, have a roof framed with trusses. The bottom piece of each truss, called the bottom chord, is buried in attic insulation, so it stays warmer and holds more moisture. The top pieces sit in the cold, dry attic air in winter, dry out and shrink slightly. That difference makes the truss arch upward in the middle, sometimes by a quarter inch or more.

The ceiling drywall is fastened to the bottom chords. Where the ceiling is also fastened to the top of an interior wall, something has to give when the truss lifts, and it is the taped joint in the corner. The result is a crack or a lifted gap along the ceiling line, often across the middle of the house, that reappears every winter.

Truss uplift or settlement?

The two look different, and telling them apart saves a lot of worry:

• Truss uplift: a straight crack along the ceiling line at interior walls, usually near the middle of the house. It opens in the cold months and closes in the warm ones. Doors and windows work normally.
• Settlement: diagonal cracks running off the corners of doors and windows, cracks that keep getting wider, doors that stick or will not latch, and gaps that do not close with the seasons. That pattern points to foundation movement, which is common on the expansive clay soils around San Antonio, Austin and the Hill Country, and it is worth having a foundation professional look at it.

How it is fixed properly

Re-taping the corner does not last, because the next winter lifts the trusses and tears the new tape. A lasting repair lets the ceiling float instead of pinning it to the wall:

• The ceiling drywall near the wall is released from the top of the wall, so it hangs only from the trusses and can move with them.
• Where the ceiling needs support along the wall, it is held with clips that let the truss move up and down without pulling on the board.
• The corner is finished so the movement does not show, for example with a trim or crown piece fastened to the ceiling only, so it slides up and down past the wall.

New construction often uses truss clips at interior walls for exactly this reason. In an existing home, the repair is done from the room side, then the corner is re-taped or trimmed and the texture is matched to the surrounding ceiling.