Spot Bonded Wall Tile in Showers, Can Thermal Imaging Help?
Using thermal imaging.
Spot bonding is the practice of installing thin-set mortar in a way it was never intended. Installers apply the mortar in dabs or globs and press the tile onto the substrate. This action greatly reduces bond strength, and sets the shower up for failure from day 1.
Tile that is installed with spots of thin-set mortar is still as much a problem as ever. I first became aware of spot bonding in the mid 90's. After all this time, I really thought that it would fade away. I am encouraged though. There are so many more installers that I talk to and see on social media that understand and acknowledge just how foolhardy the spot bonding practice is.
Why spot bonding gets missed.
I probably shouldn't have, but I remember laughing, when a home owner said to me "Shouldn't the building inspector have caught that?" In fact, the building official certainly should have. Division 9, has never been treated with the same level of scrutiny as other divisions, a blessing and a curse. Tile work has always been under the radar as far as standards have been concerned. Not because standards don't exist, but until tile became large in size, danger wasn't really associated with it. Also, spot bonding didn't really have a place when tile was small. Smaller tiler can roll with the punches, so to speak. Large tile is much less forgiving when it comes to making a surface look flat and consistent. Spot bonding is simply a means for the unskilled or ignorant to make a buck.
Spot bonding is not always easy to identify at first glance. Thermal imaging is certainly a big help. It is however just an indication, albeit a good indication, and should be followed up whenever possible with a forensic discovery.
Most of the time spot bonding is the biggest problem, but not the only one when a bad installer employs this practice. Often corners are hard grouted, shower slope is inadequate, waterproofing is lacking, and aesthetic detail is sub par. All that aside, even if everything is perfect, the shower is a failure due to spot bonding.
Checking Tile Depth Against the Drywall.
Another indication which is not as reliable as imaging, is observing the finished termination of the tile where it meets the drywall. If your tile is 3/8ths of an inch thick, and the installer used a 1/2 inch notch trowel, it stands to reason that the finished tile face could be somewhere between 5/8ths to 3/4 of an inch from the face of the drywall. Deeper than that may indicate spot bonding. Although there are factors that could increase this depth, and before you let a chat bot come to a conclusion, talk to the installer first. If the installer can't articulate a solid reasoning for an installation's face-to-substrate depth, it's time to speak with me. Just as a note, when an installer uses a half inch trowel, it doesn't mean they are adding a half inch of mortar. Once the 1/2 inch notches are collapsed properly, often the finished thickness of the mortar is anywhere from 3/16ths of an inch to 1/4 inch thick.
Please take a look at another article I have written on spot bonding if you need further information. If you suspect your tile installer is using the spot bonding practice, you should also review this article on the Miami Sandwich. Bad installers often employ both of these troublesome practices.
I'm only an email away! fill out the contact form and we can set up a Zoom that may help to confirm your suspicions, and stop the trouble in its tracks.
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