Short answer
Painting directly over a small cosmetic crack does not repair it. Remove loose material around the crack, clean the area, fill it with a suitable repair compound, allow it to dry fully, sand it smooth and prime the repaired area where needed.
First, look at the type of crack
Very fine, stable cracks can be associated with small movements in plaster, filler or drywall joints. But if a crack is getting wider, reappears quickly after repair, is accompanied by sticking doors or windows, or the wall shows significant deformation, do not treat it as a simple cosmetic defect.
In those cases, the cause should be assessed first.
1. Remove loose paint and material
If flaking paint, loose filler or weak material remains around the crack, the new repair compound will be attached to an unstable layer. Remove loose material back to a sound edge and clear away the dust.
2. Fill the crack with a suitable material
Small wall cracks can often be repaired with an appropriate spackling or patching compound. For deeper cracks, build the repair in thinner layers rather than trying to fill the full depth in one heavy application. Allow each layer to dry before applying the next.
Some drywall cracks and seams may require mesh tape and multiple layers of joint compound.
3. Sand the surface smooth
Once the filler has dried fully, sand it lightly until it is level with the surrounding wall. Remove all sanding dust afterwards. Painting over a dusty repair can reduce adhesion and spoil the finish.
4. Prime the repaired area
Patching compounds are often more porous than the surrounding painted wall. Without primer, the repaired area can appear different in sheen or colour after painting. A suitable primer helps equalise absorption.
5. Apply the finish coat
Once the primer has dried, apply a compatible finish paint. Small touch-ups can sometimes show a difference in texture or sheen; for a more uniform appearance, repainting the wall from corner to corner may give a better result.
Common mistakes
- Trying to hide the crack with a heavy coat of paint.
- Applying filler over loose edges.
- Filling a deep crack in one thick application.
- Sanding or painting before the filler is dry.
- Skipping primer on a porous patch.
- Ignoring a crack that repeatedly returns.
When should you call a professional?
If the crack is growing, repeatedly reopening, continuing in the same direction across several surfaces, or is associated with dampness or structural movement, get an appropriate building professional to assess it before repainting.
Sources
- Benjamin Moore — How to Fix Cracks and Holes in Walls
- Sherwin-Williams — How to Prep Surfaces for Painting
- Sherwin-Williams — How to Repair Walls
https://www.sherwin-williams.com/en-us/project-center/maintenance-repair/how-to-fix-repair-walls