You’ve just finished your bathroom which can be stress or exciting time, but it’s all new. The tiles look great, and then a line appears in the grout. It’s one of the most common calls I get, and most of the time it’s always fixable so do not stress.
The short answer: new grout usually cracks for one of three reasons. Grout was used where it should have been flexible silicone, the surface underneath is moving, or the grout was mixed or cured badly. Where the crack is tells you which one you’re dealing with. If its just been finished the tiler can fill that line to the brim but once it dries, a whole might be created that the tiler couldn’t see at the time.
Why grout cracks in new bathrooms
Grout is hard and rigid. It’s great between tiles on a flat surface but can’t stretch. When something moves, even slightly, the grout is the first thing to give, even with flexible grout.
1. Grout used in corners and edges (the most common cause)
Where a wall meets a floor, or two walls meet, those surfaces move slightly against each other. These joints should be filled with flexible silicone on some but not all occasions. For me, it can come down to how a tile is laid or the surface it’s working on, which can make grout a better option but often silicone in the corners is the easiest fix
2. Movement in the surface underneath
If a crack runs across a floor or wall through several tiles, something beneath is moving. That could be a flexing floor, sheeting that wasn’t fixed properly, or a slab still settling. (THINK DRAMATIC) When there is a lot of it cracked and in a large space, that’s almost always movement underneath
3. Too much water in the mix or the clean-up
Extra water weakens cement-based grout, and washing too hard with a wet sponge adds even more. The result is grout that crumbles or develops fine cracks. This is where you often get the over night holes or cracks the tiler did not see.
4. Drying too fast
Cement grout needs to cure properly. In hot, dry or windy conditions it can dry out before it’s gained its strength. [Add how you protect fresh grout on summer jobs in Perth.]
5. Grouting too early, or poor adhesive coverage
If tiles are grouted before the adhesive has cured, or there are voids under the tiles, the grout has nothing solid to sit on.
6. Old or wrong grout
Grout past its shelf life may not cure properly. The wrong product for the joint width can also shrink and crack.
What your crack is telling you
| What you see | Most likely cause |
|---|---|
| Crack in a corner or along the floor edge | Grout used instead of flexible silicone |
| Crack running across a floor or wall through several tiles | Movement in the surface underneath |
| Many fine cracks all over | Too much water, or drying too fast |
| Crumbling grout or missing patches | Poor mix or incomplete joint filling |
| Crack with a loose or hollow-sounding tile | Adhesive problem. Call a professional. |
How to fix cracked grout
Cracks in corners and edges
If I am being honest, you should never really attempt to fix these cracks if your tiling is still under warranty. If you go too far you might damage the waterproofing membrane if its near or in a shower area.
Below are some tips if you need to DIY.
Hairline cracks in the middle of a wall or floor
- Rake out the cracked grout.
- Vacuum the joint clean.
- Re-grout using the correct product for the joint width. A flexible or polymer-modified grout can help on surfaces that move a little, like timber floors or plasterboard.
Cracks that keep coming back
Stop patching. If the same crack returns, something underneath is moving, and you need to find out what before fixing the surface.
Is cracked grout a leak?
Not on its own. Your waterproofing is the membrane under the tiles, not the grout. But cracked grout lets water get behind the tiles, and over time that can reach the membrane and the wall behind it.
Don’t ignore it if:
- the crack is in the shower floor
- tiles are loose or sound hollow
- there’s dark staining or mould around the crack
- the crack keeps returning
DO NOT PANIC IF YOU HAVE A HOLE OR CRACKED GROUT – IT WILL OFTEN ALMOST NOT BE AFFECTING YOUR WATERPROOFING.
Is it your builder’s or tiler’s responsibility?
If the bathroom is new, possibly. Missing flexible sealant at junctions is a known workmanship issue. Take dated photos, write down when it appeared, and contact your builder or tiler in writing as soon as possible. Check your contract and warranty for time limits.
Often with cracked grout most renovators, builders or tilers will pop by and fix it.
How to prevent it
Ask your tiler these questions before the job starts:
- Will corners and edges be flexible silicone, not grout?
- Will the adhesive be fully cured before grouting?
- Is the grout being mixed to the manufacturer’s water ratio?
- How will fresh grout be protected from drying too fast?
For the grout itself, see my Ardex grout review: flexible vs epoxy. Epoxy is more crack-resistant, but it won’t solve a bathroom that’s moving. For more on what sits underneath, read my waterproofing guide. If your reno has other problems, see my bathroom renovation gone wrong page.
My simple explanation is below
FAQ
Is it normal for grout to crack in a new bathroom?
A hairline crack can appear as a new build settles. Cracks in corners in the first few months usually mean grout was used where flexible silicone should have been.
Can I just fill the crack with more grout?
For a hairline crack in the middle of a wall, usually yes. In a corner or edge, no. It needs silicone.
Why does grout crack in the corners of a shower?
Corners are where two surfaces meet and move slightly against each other. Rigid grout can’t flex, so it cracks on occasion but not always
How long should new grout last?
Properly installed grout with flexible joints in the right places should last for many years.
How much does it cost to fix?
Should be free under warranty.
Can I fix it myself?
Hairline cracks, yes. Shower corners and floors are riskier because of the waterproofing underneath. If in doubt, call a professional.
My Honest Advice
If you have a brick home I would always use grout on all your corners. Silicone gets dirty and often is so much harder to clean, so I am always having to change it over. If you have a fibro home, I would be 50/50 on whether you have grout or silicone in the corners. If you have cracked grout, I would not panic it is almost an easy fix and under warranty, but if you are worried, just send me an image to my email. I would be happy to take a look.
Disclaimer: The advice on this website is for general information only. I draw on years of experience in bathroom renovations and tiling, but every home and project is different. Always consult a licensed tradesperson, plumber, or builder before starting any renovations, installations, or repairs.
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