Just as I was finishing my cup of jo, one of the regular old-timers looked over at me and just shouted out, “They don’t build them like they used to!”         

Before I could say something he started talking about how they build houses nowadays.

He went on ranting that back in his day, a house was built to last hundreds of years and that today’s homes won’t last 20, due to poor workmanship and crap products. Not my words— yes, he did say crap. I just let him go on and on. 

Flo walked by, rolled her eyes, and poured me another cup of jo. I guess she knew I would be there for a while.

Just as I was finishing my second cup of jo my phone rang. “Stone Detective, here,” I said as I got up and walked outside. The voice on the other end was very businesslike. He identified himself as an architect involved in restoring an old building. 

He went on, telling me he was working on a capitol building that was built in 1878 and their marble flooring was popping up. This really caught my attention, considering how old the floor was. I had to see this for myself, so I asked if I could meet with them the following week to do an inspection. The capitol building was out of state so I needed to make travel arrangements, otherwise I would have asked to see it immediately.

After my flight, I found my rental car and headed over to the capitol building. I walked in the front entrance and was greeted by a committee of suits. There must have been about 10 gentleman waiting for me. They began to introduce themselves and gave me the feeling that I was there to perform some kind of miracle. 

Most of them were with the architectural firm and a few were from the capitol building, including the governor. Yes, this was such a big problem that the governor himself had to be there. (Made me feel really important, now let’s hope I can solve the problem!)

They took me over to a spot out of the main traffic and pointed to a tile that was noticeably loose. I reached in my bag and pulled out a suction cup and asked if I could pull that tile up. They gave me the go ahead. I attached the suction cup and the tile came right up without any effort.

I looked at the underside of the tile and there was no setting mortar attached. It was like it was just sitting there on a dry mortar bed. I started pulling tiles up all over the place and concluded that none of the tiles were bonded. So how could this be? This building is over 100 years old. What could cause the tile to lose its bond after 100 years?

Sometimes the best way to solve a problem is with questions. I asked how long this had been an issue. They told me within the last few months. I thought. I continued to ask questions and discovered that about 6 months ago they were doing some renovations which involved tearing out some small sections of flooring. 

OK, I thought, maybe the vibration caused the stone to debond. I asked if I could be alone to do some thinking. They handed me their business cards and told me to call them when I was done.

I walked all around the capitol building trying to figure out how these tiles could debond and none of my logic was making sense. Once the tile is bonded and bonded properly it is nearly impossible for it to debond as clean as these tiles where.

As I was walking around looking at the floor I noticed that the grout joints in one direction were very tight. So tight that you could hardly put a razor blade in the grout joints. Then it hit me. These tiles didn’t debond, they were never bonded in the first place. So why didn’t they come up before, for the last 100 plus years?

The only reason that fit the facts is they were so tightly installed against one another that they were being held down by the pressure on each tile. Kind of like a jigsaw puzzle. The demolition that began in several areas caused this pressure to release and then it was like a chain reaction.

So the next question was — why they didn’t bond? That answer was easier. I examined the setting bed and it had a mortar bed about 3 inches deep which was set on about 6 inches of a material known as pugging. Pugging is a coarse mortar. Due to how absorbent the pugging was, it could have absorbed all the moisture from the setting bed and not allowed it to bond to the back of the tile. 

In a follow up conversation with the architects, they asked me how the floor could be repaired. So I set up three test areas in an attempt to rebond the tiles. The first method used standard thin set. The second way was with an epoxy, and the third was with a new setting bed, with a full mortar.  

The test areas were evaluated for three months to see which one would be the most successful. All three ended up working, however the cheapest and fastest method was to reset all the tiles using standard thin set. Anyway, another case solved.

By the way, they debated which method to use back and forth for nearly three months. When dealing with a historic restoration project such as this, care must be taken. For example, every tile that was removed and reset had to be placed back into its original location and orientation. If you’re a restoration contractor and want to do this type of work I would highly recommend taking some training on Historic Stone Restoration.

The Stone Detective is a fictional character created by Fred Hueston, written to be entertaining and educational. He 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. You can send any email comments to him at fhueston@stoneforensics.com.