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Shower grout problem

7K views 5 replies 3 participants last post by  Reneescorner 
#1 ·
We've recently noticed that the grout in our shower seems to be turning to a liquid-paste - almost like it's melting. Any ideas as to what's happening?
 
#2 ·
If you get no responses from the tiling contractors in here, then it's something that normally never happens. In that case, it could be something abnormal with the grout.

Is the grout hard when it's dry and does it only turn soft when you're having a shower?

If so, it could be because someone decided they were going to use white wood glue as an "additive" in the grout to make it stick better. I've heard it's common for bricklayers to add white wood glue to their mortar to help it stick better when repointing brickwork. I've never understood that practice because white wood glue (aka: polyvinyl acetate) re-emulsifies if it gets wet and stays wet for any length of time. A much better choice would be a concrete bonding agent that's also a water based adhesive like white wood glue, but only has a short period of time after it dries that water will re-emulsify it. After that period of time elapses, then it's unaffected by moisture.

There's no telling what a homeowner will do. If they used white wood glue in their grout, it could be the white wood glue simply re-emulsifying due to the wet conditions. And, if it's mostly that glue that's holding the grout together, then the grout will come apart when it's wet.

There is a test for polyvinyl acetate. In the 1961's movie, the "Absent Minded Professor", Fred McMurray plays Ned Brainard, an absent minded college professor who invents a "flying rubber" which he calls "Flubber". "Flubber" was in fact a mixture of polyvinyl acetate (white wood glue) and Borax that was called "gluep" prior to the Disney movie. Since then, it's been called "Flubber" by most people.

I know that you can make flubber out of white wood glue, but I don't know whether using re-emulsified white wood glue would work. If you want to investigate further, try and get a sample of that "melting grout". You can find the recipe for making flubber here: (or just Google "Flubber")

https://www.msu.edu/~pilantpa/rubberflubber/RUBBERFLUBBER.htm
 
#5 ·
Yes, odd. I unfortunately can't say I've seen this before. There are 2 things that do come to mind.
1) The type of "grout" that was used. If it was some kind of premixed or mastic based material that someone used as grout, that could be the issue. A portland cement based grout shouldn't have this problem.
2) Cleaners. Any type of acid can eat into grout. I don't know if it can fall under the circumstances you mention with the softening/hardening situation you're seeing.

How long was the shower OK before you started seeing this occur? Did any sort of new cleaner start getting applied to the shower about the same time as the grout softened? How old is the shower?
 
#6 ·
The shower is at least 10 years old if not older. The prior owner did some remodeling and I'm not exactly sure when the shower was done. I noticed the problem with the shower about a year or so after we bought the house. So probably 2006. Cleaners - usually use scrubbing bubbles.
 
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