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

Drywall finishing is the final step that makes the difference between a professional-looking wall and one with visible seams and imperfections. Even if your taping and mudding are done carefully, sanding ensures everything blends together seamlessly. In this detailed guide, we’ll show you how to smooth drywall joints using a proven sequence of 120, 180, 240, and 320 grit sandpaper. Following these steps will leave your walls paint-ready, smooth, and flawless under any lighting.

Why Drywall Sanding Is Important

Joint compound (also called mud) is applied to cover tape, screws, and seams. But even after drying, the compound often has ridges, edges, or uneven textures. Sanding is necessary to flatten these surfaces and create invisible transitions between compound and drywall. Without sanding, paint highlights every imperfection.

Some key benefits of drywall sanding include:

• Invisible seams: Proper sanding ensures joints disappear after painting.
• Smoother finish: Paint applies evenly without streaks or bumps.
• Professional look: Even DIY projects appear like contractor-level work.
• Durability: Primer and paint adhere better to a properly sanded surface.

Understanding the Grit Sequence

Jumping straight to fine sandpaper won’t give good results. Each grit plays a role in refining the surface gradually:

• 120 grit: Removes ridges, high spots, and rough edges in dried mud.
• 180 grit: Smooths feathered edges and eliminates most scratches from 120 grit.
• 240 grit: Refines the surface for a nearly finished look, perfect for pre-paint inspection.
• 320 grit: Creates a final smoothness before priming, ensuring an invisible transition under paint.

Tools and Supplies You’ll Need

• Drywall sanding pole: For ceilings and high walls.
• Sanding block: Keeps pressure even and prevents over-sanding.
• Vacuum or dust extractor: Collects fine drywall dust as you work.
• Protective gear: A dust mask or respirator and goggles are essential.
• Work light: Angled lighting highlights imperfections that normal light hides.

Step-by-Step Guide

1. Level with 120 grit. Use 120 grit (25-pack) to knock down ridges and rough patches. Work lightly to avoid gouging into the drywall paper.
2. Smooth with 180 grit. Switch to 180 grit (50-pack). Focus on feathered edges and seams. Use long strokes to blend compound into surrounding drywall.
3. Refine with 240 grit. Apply 240 grit (25-pack) for fine smoothing. At this stage, the surface should feel consistent and ready for primer.
4. Finish with 320 grit. Complete the process with 320 grit (100-pack). This final sanding ensures no scratches or ridges will show through once painted.

Special Considerations

Ceilings: Always sand parallel to the main light source to avoid swirl marks that appear under lighting.

Small patches: Start with 120 grit only on the patch, then blend outward with 180–240 grit for an invisible repair.

Textured walls: If applying texture, you may stop at 180 grit. For smooth finishes, go all the way to 320 grit.

Pro Tips

• Work in sections so you don’t miss spots.
• Shine a light across the wall to spot imperfections before moving to the next grit.
• Vacuum and wipe down surfaces between sanding stages.
• Don’t press too hard—let the sandpaper do the work.
• Replace clogged sheets often for consistent results.

Aftercare

• Prime immediately after sanding to seal the surface.
• Use a quality drywall primer to prevent flashing (uneven paint absorption).
• Lightly scuff sand with 320 grit between coats of paint for a pro finish.

Frequently Asked Questions

• Can I skip 240 grit? It’s optional for quick jobs, but including it ensures a smoother, more professional look.
• Why do seams show after painting? Usually because the sanding wasn’t thorough enough. Re-sand with 180–240 grit and re-prime.
• Should I wet sand drywall? Wet sanding reduces dust but leaves uneven textures. Dry sanding is recommended for final prep.
• How do I avoid sanding through the paper? Use light pressure and switch sheets often. If you expose paper, apply a thin coat of mud and re-sand.
• Is dust harmful? Yes. Always wear a mask and goggles—drywall dust is very fine and irritating.

Watch & Learn

Shop drywall sanding sheets: Get 120, 180, 240, and 320 grit sandpaper in convenient packs. Shop drywall sanding sandpaper.

Closing Thoughts

Sanding drywall is often the least glamorous part of renovation, but it’s the step that ensures perfect walls. By moving carefully through 120 → 180 → 240 → 320 grits, you’ll eliminate imperfections and create a flawless, paint-ready surface. Patience pays off here—when light hits the wall after painting, you’ll be glad you took the time to sand properly.