Symptoms
- Faint raised or indented line visible along a seam, especially in certain light
- Line runs perfectly straight, following a taped seam
- More visible with satin, semi-gloss, or glossy paint than flat paint
Likely causes
- CommonJoint compound not feathered wide enoughA narrow taping job leaves a ridge that catches light.
- CommonGlossy paint sheen highlighting minor imperfectionsHigher-sheen paints reflect light in a way that makes small ridges more visible.
- PossibleHumidity causing tape to lift slightlyPaper tape can bubble slightly over time in humid conditions.
What to do
- Turn on a bright light at a low angle to clearly see the ridge or dip.
- Lightly sand the raised area smooth without exposing the tape.
- Apply a thin, wide skim coat of joint compound over the seam, feathering 8–12 inches on each side.
- Let dry completely, then sand smooth again.
- Apply a second thin coat if any unevenness remains.
- Prime the repaired area before repainting.
- Repaint with the same sheen used on the rest of the wall.
Tools and parts
- Wide taping knife (10–12 inch)
- Sandpaper
- Work light
Joint compoundSearch: “all purpose joint compound”
When to call a pro
Call a drywall finisher for a wall-wide skim coat if tape lines show throughout the room rather than in one spot.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.