How to Smooth Drywall Joints for Painting (120, 180, 240, 320 Grit Complete Guide)

Finishing drywall is one of the most important steps in achieving professional-looking walls. Even if your taping and mudding are done carefully, sanding is what makes the difference between rough patches and seamless walls. By following a simple grit sequence—120, 180, 240, and 320 grit—you can prepare drywall joints and patches for flawless paint application.

Why Drywall Sanding Matters

Proper sanding ensures that joints disappear once painted. It also prevents the common issues of flashing, streaking, and visible ridges that often show up under interior lighting. Benefits include:

• A perfectly smooth surface for primer and paint.
• Even blending of joint compound with surrounding drywall.
• Reduced risk of visible seams after painting.

Recommended Grits

• 120 grit: For initial smoothing of dried joint compound.
• 180 grit: For refining scratches and leveling feathered edges.
• 240 grit: Pre-paint smoothing for a refined finish.
• 320 grit: Final touch before priming, ensures invisible joints.

Tools You’ll Need

• Drywall sanding pole: Reaches ceilings and high walls.
• Sanding block: Keeps edges sharp without rounding corners.
• Dust mask or respirator: Drywall dust is extremely fine and harmful if inhaled.
• Work light: Angled light shows imperfections in compound.

Step-by-Step: Sanding Drywall Joints

1. Level with 120 grit. Begin with 120 grit (25-pack) to knock down high spots and rough compound.
2. Smooth with 180 grit. Switch to 180 grit (50-pack) to refine feathered edges and blend seams.
3. Refine with 240 grit. Use 240 grit (25-pack) for an ultra-smooth transition.
4. Finish with 320 grit. Apply 320 grit (100-pack) to create a paint-ready surface.

Special Cases

Ceilings: Always sand in long strokes to avoid swirl marks that show under light.

Repairs: If sanding patches, start at 120 grit only on the patch area, then blend with surrounding wall at 180–240 grit.

Textured walls: Stop at 180 grit if reapplying texture, go through 320 grit only if painting smooth.

Pro Tips

• Shine a light across the wall—if you see shadows, keep sanding.
• Don’t over-sand joints; it can expose tape and require re-mudding.
• Always clean dust before priming—use a vacuum and damp cloth.

Aftercare

• Prime immediately after sanding to lock down dust.
• Use a quality primer to prevent flashing.
• Lightly scuff sand with 320 grit between coats for best results.

FAQs

• Can I skip 240 grit? For most standard walls, yes, but including it gives a more professional finish.
• Why do my walls look streaky after painting? Likely because sanding wasn’t done evenly—re-sand with 180–240 grit.
• Should I wet sand drywall? Wet sanding reduces dust but can leave uneven spots—use dry sanding for final prep.

Watch & Learn

Shop drywall sanding sheets: Get 120, 180, 240, and 320 grit packs in 25, 50, and 100 counts. Shop drywall sanding sandpaper.

Closing Thoughts

Sanding drywall is the final step that separates a rough job from a flawless wall. By working through 120 → 180 → 240 → 320 grits, you can ensure that your walls look seamless and professional under any lighting condition. Take your time, check under angled light, and you’ll have perfect paint-ready drywall every time.