"Fuzz"= wood rot. Wood rot is from a lack of waterproofing. Lack of waterproofing is from installer error. Maybe catastrophic. The only diagnosis is through selective demolition.

My guess is that the sill is wood without waterproofing. Once moisture migrates through the grout to the wood, the wood swells and the tiles come loose. How do I know this? Same thing happened to me about 20 years ago a couple of years after a major remodel. At the time I just trusted the tile person to do it right. Now I know that is naïve. There is not an easy fix for that problem that does not involve partial demolition.

Thanks All- I had a handyman come and look and he said that the fuzz was insulation? And said he could just retile that space. Probably a bad idea right? Who would you call for this? A “tile person”?

Your handyman is a clueless doofus without a contractors license. For a reason. He can’t pass a test. He doesn’t have the knowledge.

That is rotten to the core, and requires a 100% redo. From skilled expert. A license is not any guarantee that someone knows what they are doing. You need to ask the right questions in your interview. Don’t expect this to be a cheap project. 8-11K average. Especially since that mold must be dealt with. There’s no telling how bad that is until demo is completed.

https://www.ceramictilefoundation.org/find-certified-tile-installers

https://www.ceramictilefoundation.org/homeowners-guide-to-hiring-qualified-tile-installer

“...he said that the fuzz was insulation.”

In addition to the fact that this is imaginative nonsense, ask yourself what purpose would be served by insulating a tile threshold. Or, better yet, ask the handyman and let us know...I love a good laugh.

Please do not have this person ever perform any work for you. Not only does he sound incompetent, he would make this particular problem worse. Get someone who knows what they are doing to rebuild this.

I love reading your responses. How do I ensure I’m hiring a competent tile mechanic? I’m so fearful of becoming one of these horror home reno stories. Thanks for your valuable tips!

millmacc, this is a concern in the tile industry as we hear about soooo many instances where unqualified labor is hired to perform tile work. Our industry is actually working on an initiative to expand our education outward to consumers (homeowners, GC's, designers, etc). We have greatly increased training and education WITHIN our industry but it is time to spread the message. If I were looking for a qualified tile contractor, I would start with those that belong to our industry's professional organization, The National Tile Contractor's Association (NTCA). They have a searchable feature on their website. Their website is also being updated this year to include a section for consumers. That is not to say that there aren't some good tile mechanics who are not members, but membership does often relate to industry involvement and education. There is also a certification mechanism that has been a good step forward. This is executed by an affiliate of NTCA called The Ceramic Tile Education Foundation (CTEF). They also have a searchable data base, by location, of certified tile installers. I will share a link here for an overview for homeowners on hiring a qualified tile installer. And one should keep in mind that while we hear about too many horror stories, the vast majority of tile installations are NOT the fails. People don't tend to share dilemmas about great jobs. Hope that helps. https://www.ceramictilefoundation.org/homeowners-guide-to-hiring-qualified-tile-installer

Thank you so much!