Over the years as an instructor of water damage restoration and mold remediation, during numerous restoration classes, I have received a wide variety of questions, often about quite similar situations. Recently, however, I was asked a question I had never heard before… about a situation I had never imagined: Tenting in water damaged tile!

That question is the reason for this article.

While teaching in Australia in August 2015, I was asked about a ceramic tile floor installed over a concrete slab in which the tile had “buckled up.” The ceramic tile failed just like hardwood flooring that has been wet for an extended period of time when it swells and finally heaves up.

What caused the ceramic tile to buckle? My initial reaction was to look for causes beyond the tile or slab:

  • Possibly some form of hydraulic (water) pressure under the slab had “pushed” the tiles off the floor.
  • Perhaps water had migrated through the slab from underneath and caused the mastic or thinset to lose its adhesive bond.

Both of these ideas were incorrect.

Buckled water damaged tile floor #1

The home was approximately seven years old and had experienced a significant water damage. The restoration company had performed the drying correctly; however, three months later, the floor “tented.” (The term “tenting” is used by the flooring industry to refer to the edges of tile rising up.) The restorer showed me pictures of the floor where tiles had buckled up in this way.

The damage looked much like when hardwood flooring “buckles,” as initially the water damaged tile edges rose up, then eventually the tiles “popped up.”

One possible cause for the damage was moisture rising through the slab. However, the ceramic tile floor was removed (after this failure), and the underlying slab was in perfect condition: No cracks, no seams, nothing. Other possible causes of damage were: 1) Either the ceramic tile had expanded (like wood does when it gets wet), or 2) The slab had shrunk.

In all my experience, I had neither seen nor heard of anything like this happening. I was truly baffled. This situation made no sense to me, so I discounted it as a one-off situation that did not seem to have a reasonable explanation.

Buckled water damaged tile floor #2

During an October class at the Restoration Sciences Academy campus in Nashville, a student approached me about one of his drying situations. It was virtually the same water damaged tile situation as what I had been asked about in Australia. Now, a one-time event I might have been able to discount as an unexplained episode not likely to occur again, but when I was asked about the same situation twice in three months, I had to consider something was going on which I did not understand. So I headed “back to the books” to undertake some serious research.

The science of tiles

I gleaned some science and engineering knowledge: In fact, ceramic will expand when it becomes wet, even though it has been fired in a kiln. Also, concrete slabs can expand when they become wet and shrink as they dry. The science corroborates these statements.

The science is complex, but I will try to explain it in terms that make sense to us practitioners. First of all, let me dispel some myths, replacing them with real facts:

Myths:

  • Ceramic tile is inert and not affected (in physical size) by water.
  • Concrete slabs may absorb water, but the slab dimensions do not change.

Facts:

  • Ceramic tile of any type will absorb water and, because of this absorption, expand in size.
  • Once dried, ceramic tile does not shrink back to its pre-loss dimensions; it stays in the expanded state. For this reason, ceramic tile manufacturers expect the installers to include expansion joints in the middle of any floor they install.
  • Concrete slabs will expand when flooded.
  • Unlike ceramic tile, concrete will shrink back to its original size as it dries.

This means in a water damaged tile situation involving ceramic tile installed over a concrete slab, both the ceramic tile and the slab will expand. When dried, the slab returns to its original size, but the ceramic tiles do not shrink back to their original size. When the concrete slab subfloor shrinks and the ceramic tile flooring itself does not shrink back, the resulting stress causes either the “tenting type” failure or tiles to simply crack into pieces. Some of the engineering terms used to explain this phenomenon are:

  • Absorption: The absorption of water vapor by a solid material.
  • Hydration: The capture of water molecules.
  • Chemisorption: The phenomenon where ceramic tiles that have free silica and/or silicates expand when dried.

Moisture expansion essentially is due to the chemical and physical adsorption of water on the amorphous phases within the tile body. The amount of expansion, as moisture enters into ceramic tiles, is affected by many variables virtually unknown to restorers. Some of these variables include:

  • The actual mineral composition of the tile material. (Most tile is made from clay, but the composition of individual clays depends upon where the clay comes from.)
  • The temperature at which the tile was fired.
  • The amount of time the tile was fired.
  • Whether the tile was fired a second or third time to anneal (strengthen) its internal structure.
  • Whether the top surface is glazed and, if so, what glazing compound material was used.

While the accepted science states that ceramic tile does absorb water and can expand, this expansion does not always appear to happen. Possibly the expansion is slight enough to be invisible or undetectable by normal eye sight, which then raises this question: If ceramic tile can expand, how much can it?

The science suggests expansion can be in the order of 0.9 mm for each meter of tile length (of the installed floor). Converting this to inches: 0.25 inches of expansion occurs for each 20 feet of flooring. This may seem an insignificant amount of expansion, but, if the tile is installed with no or minimal grout line spacing, then any expansion could lead to tile tenting or buckling.

Restorers beware

What does all of this mean for restorers? Most of us were of the opinion that ceramic tile is virtually inert, does not really absorb water and, if it does, dries out with no issues. This thinking is mostly true, except when it is not.

Restorers should be aware of situations, possibly rare, in which water damaged tile absorbs water, expands and does not shrink back after drying. This expansion can, in time (usually weeks to months after the event), result in the ceramic tile either rising up or buckling.

During the inspection of a water damage, can the restorer determine if this kind of tile failure is going to happen on a drying job with ceramic tile installed over a concrete slab?

The answer is no. Too many variables exist that are unknown and cannot be determined (for example, at what temperature the tiles were fired). This phenomenon does not mean that every water loss involving ceramic tile over a concrete slab needs to be removed, as this type of failure is very rare.

However, the potential for ceramic tile failure needs to be explained to insurance adjusters. Should a water damaged tile floor failure occur a few weeks after the drying job has been completed, the restoration contractor might be held responsible. Better to explain the possibility of a tile floor failing before the actual event occurs.

REFERENCES:
* Bowman, Richard. “Tile Growth: Fact or Fantasy?” Tile Today. Issue 36, 2001.
* Barrett, Bart B., and James M. Falls. Common Perils of Ceramic Floor Tile Systems. 2012.

Richard Driscoll has a B.S. in mechanical engineering from Clarkson College of Technology, an MBA from the University of Dayton and is currently working on his doctorate. He is a professor at Webster University where he provides graduate and undergraduate level lectures. He is an IICRC Certified Master Restorer, Master Textile Cleaner and an approved instructor. Driscoll has been consulted by state governments on legislation related to the cleaning and restoration industry. He also is the author and instructor for Restoration Sciences Academy’s MR-110 and MR-210 microbial remediation classes and MR-211 trauma scene clean up class. He can be reached at Richard@MayhemMishaps.com.