Dr. Frederick M. Hueston, PhD

I’ve been in the stone and tile business for over 40 years, and it still amazes me how many contractors out there don’t follow industry standards and guidelines. As an old-timer in the field, I’ve seen a lot, and it seems to be getting worse. Now, I’m not saying there aren’t good contractors out there, but I rarely get called to look at the good jobs. Today would be another one of those bonehead projects.

I got up early, as usual, and headed over to my favorite greasy spoon diner. When I walked in, Flo, the waitress, looked like she’d been crying. I greeted her and asked what was wrong. She shared that she had a tough morning with an abusive customer and just needed to let out a few tears. Interestingly, weeping was precisely what today’s call was about – or rather, the lack of it. Just as Flo poured me a cup of Joe, my cell phone rang. The voice on the other end, a frustrated tile supplier, had a customer complaining about her porcelain shower tiles changing color, blaming it on defective tiles. She wanted to hire me for an inspection to determine if the issue was with the tile or something else. Since it was going to be a slow day, I agreed to take a look after breakfast. I ordered ham and eggs, sunny-side up, from Flo. When she brought my order, I noticed the eggs were extremely runny – even they seemed to be weeping, another hint towards today’s mystery.

After finishing my breakfast, I said goodbye to Flo, gave a nod to the Admiral at the diner, and started up my old Woody to head to the site with the suspected defective tile.

Upon arriving at the address the tile supplier texted me, I was greeted by a friendly little old lady. She led me into the house and to the master bath where the tiles were installed. The shower was a typical walk-in with 12 x 24 white porcelain tiles on the wall and a mosaic tile floor. The first row of wall tiles was a shade darker than the rest, and I immediately suspected moisture. Using my trusty moisture meter, I confirmed that the darker tiles had higher moisture content than the lighter ones. The next step was to find the source of the moisture.

Having seen this many times, I had a good idea of what was happening. I reached into my tool bag, pulled out a screwdriver, removed the drain cover, and shone a flashlight inside. Immediately, I spotted the problem: the weep holes in the drain were clogged, and setting mortar was oozing out into the drain. Bingo!

I explained to the old lady, “You see, the bottom tiles are dark because they’re wet. They’re wet because the mortar bed underneath isn’t draining properly, usually due to blocked weep holes. It’s like a water traffic jam. When water can’t drain, it backs up into the tile bed, and the bottom tiles soak it up like a sponge, making them darker.”

I then explained that the installer had failed to install the drain correctly. The weep holes should have had gravel around them to allow water to drain from the setting bed, but instead, the setting mortar was placed right up against the holes.

The old lady looked like she was about to cry, herself (no pun intended). I reassured her that the tiles weren’t defective but that the installer needed to redo the floor properly. Next, I’d call the tile supplier with the good news.

Another case solved, and it was off to the next mystery in stone.


The Stone Detective is a fictional character created by Dr. Frederick M. Hueston, PhD, written to entertain and educate. Dr. Fred has written over 33 books on stone and tile installations, fabrication and restoration and also serves as an expert for many legal cases across the world.  Send your comments to fhueston@stoneforensics.com.