How to Sand Drywall Joints for a Smooth Finish (120, 180, 240, 320 Grit Guide)

Perfectly smooth drywall joints are the difference between a professional-looking wall and one that shows every seam under paint or light. Sanding is the key step to blending joint compound with the rest of the surface, but it requires the right grit progression and technique. In this guide, we’ll cover how to sand drywall joints step by step, from first pass to final polish.

Why Sanding Drywall Matters

Joint compound, or drywall mud, leaves ridges and uneven patches no matter how carefully it’s applied. Sanding ensures those joints disappear once the wall is primed and painted. Skipping or rushing this process results in visible seams, bumps, and shadows that ruin the finish.

Essential Tools for Drywall Sanding

• Dust mask or respirator
• Drywall sanding block or pole sander
• Shop vacuum with dust collection
• Bright work light to reveal imperfections
• Wet/dry sandpaper sheets

Best Grit Sequence for Drywall Joints

• 120 grit (25-pack) — For knocking down high spots and ridges.
• 180 grit (50-pack) — For feathering edges and blending mud lines.
• 240 grit (100-pack) — For refining the surface before priming.
• 320 grit (25-pack) — For ultra-smooth final passes where paint will highlight flaws.

Step-by-Step: How to Sand Drywall Joints

1. Prepare the room. Cover floors and vents, then set up bright lights that shine across the wall to highlight imperfections.
2. Start with 120 grit. Use 120 grit sandpaper to remove obvious ridges and high spots. Apply light pressure to avoid gouging the drywall.
3. Feather with 180 grit. Switch to 180 grit sandpaper to blend joint edges into the wall. Work in long, even strokes.
4. Refine with 240 grit. Using 240 grit sheets, smooth the entire surface so primer adheres evenly without highlighting scratches.
5. Final polish with 320 grit. Finish with 320 grit sandpaper for areas that will catch light, such as near windows or ceilings.
6. Vacuum and wipe. Remove all dust with a vacuum and tack cloth before priming.

Special Cases

• Wet sanding: For low-dust work, dampen fine-grit sandpaper to smooth the surface. This takes longer but reduces cleanup.
• Ceilings: Use a pole sander with 180 grit for overhead work to avoid uneven patches.
• Spot touch-ups: Small imperfections can be tackled with a sponge sanding block and 240 grit.

Pro Tips

• Always sand in circular motions or feathered strokes, not straight lines.
• Shine a flashlight across the wall to catch shadows before calling it finished.
• Do not oversand—going too deep exposes drywall paper and weakens the surface.

Aftercare

• Prime immediately after sanding to lock down dust.
• Use a high-build primer to fill micro-scratches.
• Apply two coats of paint for best coverage and durability.

FAQs

• Do I need to sand between paint coats? Yes, a light pass with 320 grit between coats ensures the smoothest finish.
• Can I use an electric sander? Yes, but keep it on low speed and use fine grits to avoid damaging drywall.
• What if I see scratches after priming? Spot sand with 240–320 grit, then touch up primer before painting.

Watch & Learn

Using the right grit sequence is the secret to invisible drywall joints. Stock up on fine grit sandpaper for your next project and achieve professional-grade walls with ease.