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We bought our house anew and didn't notice the uneven grouting job until the grout started to fall off after the first few years. My questions are

  1. I suppose I have to remove the existing grout off the tile and shower base before doing anything. Scraping with the grout removal tool takes forever and leaves leftover grout or scratches. What is the best way to clean all the grout to start afresh?
  2. What should I replace the grout with? Simple unsanded grout? Any additive? The gap seems too wide to caulk, right?

Corner

Overdone grout coming over shower base

Grout coming off corners

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  • you are looking at more serious problem then grout
    – Traveler
    Jun 5, 2022 at 3:46
  • I suggest you clean with Lime Away in addition to removing the existing caulk. Jun 6, 2022 at 5:49

2 Answers 2

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There is a crack. This is normal and expected, because grout doesn't flex. Every time someone gets into the tub, the tub will flex a small amount, and that will crack the grout. Then water gets under it, and problems start.

That's why the joints around the tub, and usually in the corner of the shower, have to be done with silicone caulk and not cementitious grout.

However a silicone caulk joint needs to be wide enough to stretch. The idea is that, if you fill a 1mm wide crack with silicone, and when you step in the tub the crack enlarges by another millimeter, that will stretch the silicone from 1mm to 2mm, or by 100%, so it will tear. But if the silicone joint is at least 5mm wide, then the stretching is a much smaller proportion of that, so it doesn't tear.

So you need to remove the cementitious grout along these joints first. You can use a scraper, a painter's tool, whatever works.

Then you need a tool like this to apply the silicone:

enter image description here

Basically if you use your finger, you'll push the caulk into the joint and make it "hollow" (right) and it won't last. If you use the proper tool, the caulk will cover the top of the tile over a few mm (red arrow) and it will have much better adhesion.

enter image description here

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    Fill the bathtub with water before you put in the new silicone caulk. The weight of the water will help to pull the gap open to allow the caulk to adhere when more weight is added and compress when the tub is empty.
    – gnicko
    Jun 6, 2022 at 14:35
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So short of resolving any mold issues, which there likely is. I had similar issues with the house I just bought, I would make sure that the wood under the tub isn't starting to rot. But in the meantime, scrape away what is there and wipe it down so it's clean and caulk is fine to no that is not too big of crack just make sure you get the one that says for tub and shower and you are good to go. Takes an hour or so to dry all the way.

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