Home of The Stone Detective
The Case of the Hollow floor
It was nearly closing time at Flo’s Diner. The dinner crowd was gone, the chairs were being turned upside down on the tables, and Flo was wiping the counter with a rag that had probably been there since Truman was president.
The Admiral and I were playing checkers in the corner booth.
“You’re cheating,” he said.
“I’m investigating.”
Just as I was about to take his last king, the front door opened. A nervous-looking man stepped inside carrying a marble tile under his arm.
“Which one of you is the Stone Detective?” he asked.
Flo pointed at me.
“He’s the one wearing a fedora indoors.”
The man introduced himself as Mr. Harris. He’d recently had a white marble floor installed, but several tiles sounded hollow when he walked across them. The installer said the sound was normal.
Normal is a word people use when they hope you’ll stop asking questions.
I grabbed my inspection bag, climbed into my old 1946 Ford Woody, and followed Mr. Harris across town.
Tapping Out the Truth
The marble floor looked beautiful. Smooth, polished, and innocent. Most suspects look innocent until you start tapping on them.
I used a small tapping tool to check the floor. Some tiles produced a solid sound. Others answered with a hollow thud.
The pattern told me what was hiding underneath.
The installer had placed several large spots of mortar on the backs of the tiles instead of spreading the mortar evenly. This left empty spaces beneath the marble.
“Will the floor fail?” Mr. Harris asked.
“Maybe not today,” I said. “But the tiles aren’t properly supported.”
What’s Really at Risk
A heavy load placed over one of those voids could crack the marble. Moisture could also collect beneath the tiles, causing:
- Dark spots
- Staining
- Eventual debonding
Natural stone requires proper mortar coverage, especially along the edges and corners. Spot bonding may save an installer a little time, but it can leave the homeowner with years of trouble. And, give the installer alot of callback headaches down the road.
Case Closed, Checkers Unfinished
Later that evening, I returned to the diner. Flo had locked the door, but the Admiral was still staring at the checkerboard.
“What was wrong with the floor?” Flo asked.
“It was full of empty promises.”
The Admiral moved one of my checkers when he thought I wasn’t looking.
“Hollow promises,” he said. “Sounds like a politician.”
Another case solved, and I still had a checker game to finish.
