Why Is My Grout Cracking? 5 Causes and the Fix That Lasts

Grout cracking is a failure of the cement joints between tiles, and it almost always means something is moving, too wide or mixed wrong. So why is my grout cracking? The usual causes are movement, the wrong grout for the joint width, and grout in corners that need caulk. A floor that flexes under your feet is another. Even brand-new grout cracks when one of these is present. The fix that lasts starts with finding which one you have.

Key Takeaways

• Cracks follow movement: grout is rigid, so anything that shifts under or behind the tile cracks it.
• Corners should be caulk: a straight crack down a shower corner means grout was used where silicone belongs.
• Floor cracks point down: cracks running across a floor usually follow a joist, plywood seam or slab crack.
• Joint width matters: joints 1/8 inch and wider need sanded grout. Unsanded grout shrinks and cracks in wide joints.
• Cost: full regrouting runs $5-$24 per sq ft (as of 2026 pricing).

This spoke answers one question. Go Back to regrouting shower tile for the full process, or see the shower tile repair Complete Guide.

Why Does Grout Crack, Even New Grout?

Grout cracks because it is hard and brittle, and the things around it move. When a wall, floor or tub shifts even slightly, the grout takes the stress and breaks. New grout can also crack from how it was mixed or packed.

The 5 most common causes

1. Movement. Framing dries out, houses settle and walls swell with humidity. In Greater Boston, winter temperature swings add to it.
2. Wrong grout for the joint. Unsanded grout is made for joints under 1/8 inch. In wider joints it shrinks as it cures and cracks down the middle.
3. No movement joints. Corners, the tub line and room edges need flexible sealant. Grout in those joints cracks first.
4. Floor deflection. A floor that bounces flexes the tile and snaps the grout between it.
5. Thin or watery grout. Too much water in the mix makes weak grout. A thin skim over old grout has nothing to hold onto.

Is It Normal for New Grout to Crack?

No. New grout should not crack. Hairline cracks in the first weeks usually mean too much water in the mix or the wrong grout for the joint. Cracks only in the corners mean a missing movement joint. Cracks in a line across the floor mean the floor is moving.

Seeing cracks you can't explain? Get a free estimate for your cracked shower or floor grout: send photos of the cracks and a wide shot of the room for a same-day quote.

Why Is Grout Cracking in Shower Corners?

Grout cracks in shower corners because corners should be caulked, not grouted. Two walls meet there and each one moves on its own. Rigid grout in that joint breaks in a straight line from top to bottom.

The TCNA Handbook movement joint method, EJ171, calls for flexible joints at every change of plane. That means inside corners, the floor-to-wall joint and the line where tile meets the tub. A tub drops a little when it fills, so grout along the tub line cracks too. Our guide on caulk vs grout in shower joints shows exactly where each one belongs.

Signs your corner crack is just a caulk problem

• The crack runs straight down the corner and nowhere else.
• The tiles on both walls sound solid when tapped.
• There is no stain on the ceiling below or soft spot in the wall.

If the tiles sound hollow or the wall feels soft, water has likely gotten behind the tile. Read about a shower leaking behind wall before you regrout.

What Does Grout Cracking Across a Floor Mean?

Grout cracking across a floor usually means the subfloor or slab is moving. The crack follows whatever is below it. That can be a joist, a seam in the plywood or a crack in the concrete.

Per the TCNA Handbook and ANSI A108 standards, a floor under ceramic or porcelain tile should not flex more than L/360 under load. Natural stone needs L/720, which is twice as stiff. A floor that misses those numbers keeps cracking grout no matter how many times you patch it. Tap the tiles along the crack. A hollow sound means the tile lost its bond, and our cracked tile repair guide covers what comes next.

Where the crack is and what it tells you

If floor tiles feel loose as well, read our guide on a loose bathroom floor tile.

How Do We Fix Cracked Grout for Good?

We fix the cause first, then regrout with Laticrete Permacolor and put flexible sealant at every change of plane. Regrouting without fixing the cause just resets the clock. Here is the order we follow on the jobs we've done since 2016.

1. Find the cause. We tap every tile and check corners, the tub line and the floor for movement.
2. Cut out the old grout to at least 2/3 of the tile thickness. New grout needs depth to hold.
3. Pick the right grout. Sanded for joints 1/8 inch and wider, unsanded for narrower joints.
4. Regrout with Laticrete Permacolor, packed firm and mixed to the right water ratio.
5. Caulk every change of plane with silicone color-matched to the grout.
6. Seal cement grout. A penetrating sealer protects it for 1-3 years.

Cement grout vs epoxy grout

• Laticrete Permacolor (cement): about $2 per sq ft in material. Needs sealing every 1-3 years.
• Laticrete SpectraLOCK or Mapei Kerapoxy (epoxy): about $5 per sq ft in material. Stain-proof and never needs sealing. A strong choice for busy shower floors.

Full regrouting runs $5-$24 per sq ft based on current Greater Boston rates, and most jobs take 1-3 days. If we find water damage or a weak floor, repair work runs $10-$50 per sq ft. On new floors we set tile over Strata Mat uncoupling, with 254 Platinum thinset under the mat and 253 Gold over it. That mat absorbs the movement that cracks grout.

Can You Just Patch Cracked Grout?

You can patch a few small cracks, but the patch rarely matches and often cracks again. New grout next to old grout looks different, even in the same color. If the cause is still there, the patch fails along the same line.

Stop the Cracking at the Source

Why is my grout cracking? Because something is moving, or the wrong material is in the joint. Fix the movement, caulk the corners and use the right grout, and the cracks stop. Aguirre Modern Tile is a registered Massachusetts home improvement contractor (HIC #655072) and fully insured.

Tired of grout that keeps cracking? Send photos to Aguirre Modern Tile and get a same-day estimate to fix the cause, not just the crack.