Symptoms
- Diagonal crack starting at the top corner of a door or window
- Crack often 45 degrees, a few inches long
- Doors and windows still open and close normally
Likely causes
- CommonStress concentration at frame cornersCorners are weak points where drywall seams meet, so minor house movement shows up there first.
- CommonNormal seasonal house movementWood framing expands and contracts, which repeatedly stresses these corners.
- Less commonFoundation or structural settlingIf the crack is wide, growing, or the door/window binds, it can point to bigger movement.
What to do
- Check that the door or window still opens and closes smoothly without binding.
- Apply self-adhesive fiberglass mesh tape diagonally over the crack.
- Cover with a thin layer of joint compound, feathering the edges.
- Let dry completely, then sand smooth.
- Apply a second thin coat if needed for a flush finish.
- Prime the patched area before painting.
- Repaint to match the surrounding wall.
Tools and parts
- Taping knife
- Sandpaper
- Utility knife
Fiberglass mesh tapeSearch: “self-adhesive fiberglass drywall tape”
When to call a pro
Call a foundation contractor if the door or window sticks, the crack keeps widening, or you see similar cracks throughout the house.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.