How to Check Grout and Caulk

Your tile shower or tub surround looks solid, but it’s only as good as the grout and caulk holding it together. Those materials are what keep water from getting behind the tile and into your walls. When they fail—and they will fail eventually—you’re looking at rotted studs, moldy drywall, and expensive repairs.

Why This Matters

Tile is waterproof. The spaces between tiles are not. That’s what grout and caulk are for. But both degrade over time:

• Grout cracks – From movement, settling, and impact
• Caulk peels – From age, moisture, and poor adhesion
• Water gets in – Through gaps you can barely see
• Mold grows – In dark, wet wall cavities
• Wood rots – Structural framing behind tile
• Tile loosens – When the backing fails

The scary part: damage happens slowly, invisibly, until suddenly you have a major problem. Regular inspection catches issues early.

Where to Check

Focus on wet areas—showers, tub surrounds, and backsplashes near sinks:

Tub and Shower Corners

Where walls meet the tub or shower base, and where walls meet each other. These are movement points where caulk is used, not grout.

Tile-to-Tub/Shower Pan Joint

The bottom row of tile meets the tub or shower base. This joint takes the most abuse and fails most often.

Around Fixtures

Where faucet handles, spouts, and shower heads penetrate the tile. These are penetration points for water.

Grout Lines Between Tiles

All horizontal and vertical grout lines, especially at the bottom of shower walls and directly behind sinks.

Floor Corners

Where tile floors meet walls, vanities, or tubs.

What to Look For

Grout Problems

• Cracks – Even hairline cracks let water through
• Crumbling sections – Grout powder coming out
• Missing sections – Holes or gaps in grout lines
• Discoloration – Dark spots that won’t clean off
• Soft texture – Grout should be hard; soft means water damage
• Hollow sound – Tap gently; hollow means tile has separated from backing

Caulk Problems

• Peeling or lifting – Pulling away from one or both surfaces
• Cracking – Splits through the caulk bead
• Mold or mildew – Black or dark staining
• Gaps – Visible openings between caulk and surface
• Soft or mushy texture – Indicates water behind the caulk

Signs of Deeper Damage

If you see these, water has already gotten through:

• Soft spots in the wall when you press
• Loose or hollow-sounding tiles
• Dark staining on the back of tile (visible if one is loose)
• Water dripping or staining in the room below
• Musty smell in the bathroom

The Water Test

Not sure if grout is failing? Use the spray bottle:

1. Spray water along grout lines
2. Watch for bubbles or absorption
3. Healthy grout should bead up or sit on the surface
4. Water that absorbs quickly or bubbles indicates porosity

Step-by-Step Inspection

1. Visual Check

Stand back and look at all tile surfaces. Note any obvious discoloration, cracks, or gaps.

2. Get Close

Get down to tile level. Run your fingers along grout lines. Feel for cracks, soft spots, or crumbling.

3. Check Caulk Joints

Press gently on caulk in corners and at the tub/shower base. It should be firm and adhered to both surfaces.

4. Tap Tiles

Gently tap tiles with a knuckle or plastic tool. Solid tiles sound solid. Hollow sounds indicate separation from the backing.

5. Look Behind Escutcheons

Remove faucet handles or spout escutcheons if possible. Check for water stains or damage behind them.

Minor vs. Major Problems

Minor (DIY Repairs)

• Isolated grout cracks in non-critical areas
• Small sections of failed caulk
• Surface discoloration without underlying damage
• Sound tiles with minor grout damage

Major (Investigate Further)

• Multiple loose tiles
• Soft wall surfaces
• Water stains in rooms below
• Extensive mold in grout lines
• Large sections of failed caulk with visible gaps

DIY vs. Call a Pro

DIY: Re-caulking tub surrounds, repairing small sections of grout, routine inspection.

Call a pro: Extensive tile damage, suspected water damage behind walls, mold remediation, full shower or tub surround replacement. Find a handyman →

How Often to Check

• Quick check: Monthly, while cleaning
• Full inspection: Every 6 months
• After any repair: Verify the fix is holding

The Bottom Line

Grout and caulk are cheap. Rotted walls and mold remediation are not. Spend twenty minutes twice a year really looking at your tile work. Fix small problems before they become big ones. It’s the most cost-effective waterproofing you can do.