How to Get Rid of Mold in a Shower + Prep Walls for Tile

I finally learned how to get rid of mold in a shower and prep the walls for tile. Before the pretty part, I had to deal with the not-so-pretty part: mold. With a whole lot of research and a little expertise from my contractor father-in-law, I found that gutting and re-doing a shower is a lot less intimidating than it looks. Here’s how I removed the mold, rebuilt the walls correctly (including a quirky window situation), and waterproofed everything so it’s ready for tile.

This post takes you from demo to fully waterproofed walls – the exact stopping point before tile. When you’re ready to set tile, go to How to Tile a Shower.

Here’s what I started with. The tile and caulk were stained, the grout was failing, and water had clearly been sneaking behind the walls for a while. This is definitely a “pull it all out and start fresh” kind of fix.

Below is my step-by-step on how to get rid of mold in a shower and prep the walls for tile.

Tools for Removing Shower Mold and Prepping Walls for Tile

• Safety glasses, N95 or respirator, gloves
• Utility knife, pry bar, hammer, oscillating multi-tool
• Tape measure, stud finder, level, laser level
• Drill/driver + cement board bit
• Buckets, scrub brush, sponges, rags
• Paint roller and brush for waterproofing membrane

Materials for Removing Shower Mold and Prepping Walls for Tile

• Plastic sheeting and painter’s tape for basic containment
• At home mold test kit
• Mold cleaner and white vinegar
• 1/2 inch cement board + cement board screws
• Yellow alkali-resistant mesh tape for seams
• Waterproofing membrane paint and seam fabric/tape
• lumber for framing a shower niche
• Plumbing valve and trim kit (I used the sponsored Karci Pfister Faucet and loved the quality)
• Heavy-duty trash bags

Step 1: How to Get Rid of Mold in a Shower (Safety First)

Shut the bathroom door, crack a window if you can, and get a little airflow going. Pop on gloves, eye protection, and an N95. If anything looks big or suspicious, get it tested and call a pro. Otherwise, take it slow and work carefully with your safety gear on.

Step 2: Remove Tile & Wet Greenboard (Start Shower Mold Removal)

I started popping off the original shower tile and discovered lots and lots of mold. The tiles came off way too easily because the greenboard behind them was very wet. Debris went straight into contractor bags so it didn’t travel through the house.

Greenboard vs. cement board in showers

Greenboard is moisture resistant, not waterproof. It’s fine for damp bathroom walls. It’s not a proper substrate inside the shower where it takes direct water. In wet zones you want a cementitious backer like 1/2″ cement board, screwed into studs. Cement board stands up to water exposure; the waterproofing membrane on top is what actually stops water from getting into the wall. That two-part system is what you want behind tile.

Step 3: Clean, Treat, and Dry the Framing

I doused the framing with Mold Armor, scrubbed, then followed with warm water and white vinegar. After cleaning, I let the wall cavities dry completely. Give it time – trapped moisture is how problems sneak back in and why you see mold in shower walls.

Step 4: Build and Pitch the Shower Niche

With everything clean and dry, I built my custom shower niche between studs and aligned it with my future tile layout. Fun backstory: this window used to look outside. Years ago a room addition turned this into an interior window, so the ‘view’ is just drywall on the other side.

How I built the niche frame (quick guide):

1. Layout: Measured bottle height and picked a width that lands neatly on tile joints.
2. Cut parts: From 2x4s, cut two verticals, a top and bottom shelf piece, and short returns for the sides.
3. Assemble in the wall: Fastened the bottom piece first between the studs, then the top piece, so the niche is boxed in.
4. Pitch for drainage: Shimmed the bottom 2×4 slightly forward (about 1–2°) so water runs out of the niche, not back into the wall.
5. Prep for sheathing: Added small corner blocks so the cement board edges around the niche have full support.

With the niche framed and pitched, I moved on to hanging cement board.

Step 5: Install 1/2″ Cement Board (Prep Walls After Mold Removal)

With everything clean and the niche built, I started by dry-fitting 1/2″ cement board to plan seam locations and confirm the niche/window cutouts lined up, then hung the panels.

What I did:

• Fastened cement board every 7–8 inches into existing studs.
• Kept factory edges together when I could for straighter seams.
• Left the small manufacturer-recommended gap at the tub flange.
• Cut clean openings for the valve, shower arm, niche, and window.
• Dry-fitting first helped me map out seams and confirm niche/window cutouts before committing-huge for anyone learning how to get rid of mold in a shower and rebuild correctly.

Once the big panels were up, I checked for any seams or edges that felt bouncy. Those spots are where additional blocking makes a huge difference.

Step 6: Add Additional Framing & Blocking

After a few panels were on the wall, I could see where the old framing didn’t land perfectly at sheet edges. Some seams flexed when I pressed on them – that’s my cue to add blocking so every edge has solid screw bite and the wall feels rock steady for tile.

How I retrofitted blocking (without tearing everything down):

1. Mark the flexy seams: I pressed along panel edges and seams. Anywhere I felt movement, I marked the line with a pencil.
2. Use openings to your advantage: I slipped short 2×4 blocks on the flat through the niche and window openings (and the top if the ceiling was open).
3. Clamp & screw from the front: I held the block tight behind the seam, then drove screws from the cement-board face into the block so the seam now had solid backing. Where it helped, I added a dab of construction adhesive behind the block.
4. Sister where needed: If a stud was out of line or too far from a seam, I sistered a new stud to bring the face flush.
5. Corners & transitions: I added short blocking at outside corners and the tub leg so trim and tile edges won’t flex later.

Why this matters: Backer that flexes = lippage, cracked grout, and sad tile. Solid backing every 7–8 inches gives you flat, strong walls and clean grout lines.

Step 7: Tape Seams with Alkali-Resistant Mesh and Thinset

I used alkali-resistant fiberglass mesh tape on every seam and inside the niche corners, then skimmed thinset to embed the tape. I also hit all the screw heads with a light coat. Let that dry before moving on.

Checkpoint before waterproofing

At this point everything was dry, solid, and flat: cement board up, seams taped, screw heads covered. That’s your green light to waterproof.

Step 8: Waterproofing the Shower Before Tile (Two Coats)

Now for the satisfying part. I rolled on two full coats of waterproofing membrane, embedding fabric where required and giving extra attention to corners, the niche, and the window recess. Follow the dry time on the label between coats.

Was it necessary to paint the entire thing and not just the seams? I’m thorough, so I coated everything – it didn’t feel right leaving any cement board un-green. Now I know it’s watertight.

Step 9: Final Checks Before Tile

Look closely at corners, seams, and every plumbing penetration. Touch up any thin spots. Once the membrane cures, your shower is ready for tile and we can move to Part 2.

Why Showers Get Mold

Most shower mold comes from slow water intrusion – cracked grout, unsealed corners, a poorly detailed niche or window, or skipping the waterproofing membrane. Moisture sneaks behind tile, saturates greenboard, and the bond fails. Rebuilding with cement board plus a full-coverage membrane is the fix that lasts.

Black Mold in Shower: What to Know

• Color alone doesn’t prove toxicity. Test if you’re concerned.
• Don’t mix chemicals. Never mix bleach with vinegar or ammonia.
• If the contamination is widespread or you feel in over your head, it’s worth calling a remediation pro.

Pink Mold in the Shower: Causes and Cleanup

“Pink mold” is usually a biofilm that loves soap residue. Clean with your favorite bathroom cleaner, rinse well, and keep surfaces dry. Long term, the fix is the same: rebuild correctly and waterproof.

Pro Tips

• Let framing dry fully before you rebuild.
• Cement board in the wet zone, always.
• Use alkali-resistant mesh tape – drywall tape won’t cut it here.
• Two full coats of membrane create a continuous shell.
• Slightly pitch niche shelves to drain.
• Save silicone for change-of-plane joints later. Don’t grout corners.

Common Mistakes

• Leaving damp framing or insulation in place
• Using greenboard or regular drywall inside the shower
• Skipping seam tape or using standard drywall tape
• Only spot-coating seams with membrane
• Forgetting to check coverage inside the niche corners

Troubleshooting

• Musty smell after demo: Keep fans running and check adjacent cavities for hidden moisture.
• Soft studs: Replace damaged framing before cement board goes up.
• Streaky membrane: Add another coat after the recoat window.

If you followed these steps, you’ve learned how to get rid of mold in a shower, rebuilt with cement board, and created a waterproof shell.

What’s Next: Tile the Shower

Waterproofing is done, seams are sealed, and the niche is framed. Time for the fun part. Head to How to Tile a Shower for layout, tile placement, laser lines, ledger boards, grout, and silicone.

Related Tutorials

• DIY Gold Bathroom Mirror (Easy Rub ’n Buff Makeover)
• DIY Board and Batten Wall in a Bathroom: Beginner Guide
• How to Install a Toilet: A DIY Step-by-Step Guide

Pinterest: Save This Project for Later

Pin now and come back when you’re tackling shower mold and prep.