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Unread 03-25-2021, 09:45 AM   #1
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Hairline cracks in new shower grout

We just had a new tiled shower put in a week ago. They used poly blend sanded grout. Now we have noticed hairline cracks and pinholes in the grout. There are also places where the grout looks darker/dirty. The contractor said they will come back and use an epoxy stain to make the color on the grout look the same throughout. I’m more concerned about the hairline cracks. How should the cracks be fixed? Do they need to take 2/3 grout out and regrout or are there other options? Once the epoxy stain is applied do I still need to seal the tile? The second pic shows one of the hairline cracks. The third pic shows the dark/dirty grout.
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Unread 03-25-2021, 02:12 PM   #2
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Welcome, Jana.

Cracking grout is usually caused by movement in the tile installation. Knowing more about how the shower was constructed and how it was waterproofed would be helpful. I'm not familiar with the pink wallboard in your first photo, but perhaps others may be.

A photo or two from farther away to give some perspective would also help, with marking or description of the location of the cracked grout.

Were the vertical corners and other changes of plane in the tile installation grouted with the same material?

The darker areas in the light grout could be from the joints not having been properly cleaned before grouting if a gray mortar was used for bonding the tiles. That said, Polyblend has a history of not always curing to a consistent color, but in my experience that's usually with the darker grays and browns and the splotchy areas are lighter rather than darker.

The "epoxy stain" is probably not epoxy and probably not a stain, but rather more of a paint type material. Some of them work well if properly applied, but can be problematic in wet areas.

There is no "need" to seal anything in that shower that I can see. The glazed tiles will accept no sealer at all, nor will the grout joints after the "stain" has been applied.

My opinion; worth price charged.

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Unread 03-25-2021, 05:43 PM   #3
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Hairline cracks in new shower grout

The old shower was a shower kit/insert. They took that out and constructed the new tiled shower. I’m not sure how the shower was waterproofed and constructed. All of the hairline cracks seem to be horizontal on the walls, none are vertical. The cracks are in the middle section of the walls not the top or bottom of the walls. I’m not sure if the corners were done with the same sanded grout but I included a pic of the corner. I just want to try and figure out the best way to fix the cracked grout before they come back to finish the work. What are my options?

Should the grout be sealed before the epoxy stain is applied or the epoxy stain is enough?

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Unread 03-25-2021, 10:11 PM   #4
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To my eye, the wallboard appears to be HardieBacker Cement Board with HydroDefense. The joints/seams and fastener penetrations still must be waterproofed. It seems there is some sort of liquid applied waterproofing on the walls, but I find it odd and worrying that the niche doesn't appear to have proper waterproofing on the seams and fasteners too.
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Unread 03-26-2021, 06:14 AM   #5
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I don't see any mesh tape on the seams. That alone would produce the cracks in the grout. They aren't going away without it.
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