Drywall Finishing Mistakes: What I've Done Wrong and Learned

Published December 25, 2024 by Mike Sullivan

Key Takeaways

  • Rushing between coats causes most finishing failures
  • Over-sanding removes material you'll just have to reapply
  • Too much compound builds up and creates more work than too little
  • Inconsistent lighting while working hides problems that appear later
  • Most mistakes are fixable with additional coats and sanding

Every drywall mistake I've made has taught me something. The basement with visible seams everywhere taught me about proper feathering. The bathroom with bubbled tape taught me about bed coats. The ceiling that took six coats taught me that patience in early stages saves time later.

Here's a collection of mistakes, mostly mine but some from friends and family who've shared their learning experiences. The common thread is that most of these are preventable with knowledge and patience.

Rushing Between Coats

The most common mistake. You want to finish the room, the first coat looks dry, why wait?

What happens: The surface feels dry but moisture remains inside. Your second coat seals that moisture in. It can't escape. The compound stays soft, cracks, or bubbles as trapped moisture tries to get out.

I once did three coats in a day because I had setting compound and thought I could push through. The seams looked fine at first. Within a week, fine cracks appeared along every joint where moisture had been trapped.

Prevention: Let each coat dry completely. Touch it. It should be completely hard, not just surface dry. When in doubt, wait another day.

Over-Sanding

Sanding feels productive, so people over-do it. Especially on seams they're frustrated with.

What happens: Sand too much and you go through the compound to the tape. Or you sand through the tape to the paper. Now you've created damage that needs another coat to repair.

I sanded through paper trying to fix a butt joint that wouldn't disappear. Made it worse. Had to apply compound over the damaged paper, let dry, then start the feathering process again.

Prevention: Light pressure. Use fine grits. Check frequently. If the seam isn't going away with sanding, the problem is the mud work, not insufficient sanding.

Too Much Compound

Beginners often apply compound heavily, thinking more coverage means better results.

What happens: Heavy coats take forever to dry. They shrink more, causing cracks. They build up seams into visible ridges. You end up sanding off most of what you applied.

My first finished room had seams that stood proud by 1/8 inch. I thought that was normal. It's not.

Prevention: Thin coats. Apply just enough to cover, then feather. If the tape is visible through your first coat, that's fine, that's what subsequent coats are for.

Insufficient Feathering

Feathering is what makes seams disappear. Without it, you have visible ridges.

What happens: Compound ends in an abrupt edge instead of gradually thinning to nothing. That edge is visible, especially in raking light. Paint highlights it.

I thought feathering was just running my knife outward. But I wasn't actually reducing the compound thickness. My seams had sharp edges that showed through paint.

Prevention: Each coat should be wider than the previous. The outer edge should be so thin you can barely tell it's there. Run your hand across it. You shouldn't feel a bump where the compound ends.

Wrong Compound for the Job

Different compounds have different purposes. Using the wrong one creates problems.

What happens: Topping compound for tape embedding results in weak bond and tape failure. Setting compound for final coats is harder to sand. All-purpose for everything works but isn't optimal for any stage.

I once used leftover topping compound to embed tape because I didn't want to buy new mud. The tape bubbled within months because topping compound doesn't bond as strongly.

Prevention: Use tape-strength compound (all-purpose or setting) for embedding. Use easier-sanding compound (lightweight or topping) for final coats.

Bad Lighting While Working

Room lighting hides imperfections. You finish a wall, it looks great. Then sunlight hits it at an angle and every flaw appears.

What happens: You miss high spots, holidays (missed areas), and feathering problems because the work light or room light doesn't reveal them. After painting, they're obvious.

This happened in our living room. Finished, painted, looked good until afternoon sun hit the wall at a low angle. Every seam visible.

Prevention: Use a bright work light at a low angle while finishing and sanding. Check from multiple angles. Fix problems before painting, not after.

Bubbles in Tape

Air trapped between tape and drywall creates bubbles that show through and eventually fail.

What happens: Not enough bed coat or not pressing firmly enough traps air. The bubbles might not show immediately but they're weak points that crack and peel over time.

First tape job I did had bubbles everywhere. Didn't notice until they started cracking through the paint.

Prevention: Sufficient bed coat. Firm embedding pressure. Watch for bubbles as you embed and press them out. If you see one forming, stop and fix it immediately.

Skipping Primer

People skip primer to save time or believe paint-and-primer combinations work. They don't on new drywall.

What happens: Compound absorbs paint differently than paper. Seams appear as dull or shiny areas after painting. This is called flashing.

My first paint job had obvious flashing. Had to sand, prime properly, and repaint. Took twice as long as doing it right the first time.

Prevention: Prime new drywall with actual primer, not paint-and-primer combo. PVA primer is made specifically for this and isn't expensive.