Cork Flooring Problems: My Cork Tiles Won’t Stick!

cork flooring installation | @GlennRevere

As a Certified Flooring Inspector, my job is to look at flooring installation failures and figure out what happened. Some people say I am a forensics flooring failure person. I look at all kinds of flooring. Today’s Inspection Safari is about a glue-down cork tile floor that wouldn’t stick to the concrete subfloor.

As with any flooring material, cork tiles must be installed according to the manufacturer’s specifications. Each brand has its own requirements. You can’t necessarily install Brand X the way you did Brand Y. That is why installation instructions are included with every box of material. Unfortunately, some installers think you CAN install different brands the same way and get the same results. It doesn’t work that way.

I was asked to inspect a 12” X 12” solid cork tile glue-down job a month after it was installed. The cork had begun to lift off the concrete subfloor after one day. The homeowner was very upset!

loose cork tile | @GlennRevere

This installation was the final phase of a home remodel. As part of the remodel, the back patio had been removed. A new, larger one had been poured, finished, enclosed and incorporated into the existing family room. The cork tiles were installed throughout this single story home: front entry/closets; hallway; three bedrooms; and combined kitchen/family room — almost 1,700 square feet of parquet tiles. The tiles were firmly attached everywhere except over the new patio subfloor.

The installer met me at the job site. He explained that the adhesive manufacturer required a new slab to dry out for at least 28 days. They had waited 45 days. Then he used a concrete moisture meter on the slab subfloor throughout the home before installation. His meter indicated very low moisture readings. (He did not write down and save the readings, as required). He had stored the boxed tiles in the garage for three days before he installed them. He applied the adhesive according to the instructions, laid the floor, and rolled the tiles using the correct type and weight of roller. He couldn’t figure out why the tiles over the new patio wouldn’t stick while they were stuck tight everywhere else. He also noticed that it smelled moldy under the tiles when he removed a 10’ X 12’ section from the patio.

The first thing I did was to take my own concrete moisture readings. I found exposed original concrete in the front hall closet. The metering scale runs from “0” to “6”. Anything below 4.5-5 for the adhesive used is OK. The reading was 3.5. Then I took a reading on the recently poured patio concrete. The reading was 6 — the highest possible! A reading this high means that the concrete is practically swimming in water — lots of water vapor coming up from the slab. I could have stopped the inspection then. There is no way that any adhesive will hold flooring down under these conditions. But I continued my inspection.

concrete moisture meter | @GlennRevere

Each manufacturer has their own specification for acclimating the flooring materials prior to installation. This means that the materials have time to adjust to “average in-use conditions” — the normal temperature and humidity in the home — before the materials are laid. The cork had been stored in the garage for three days before installation. It should have been stored inside the home with the temperature and humidity at normal living levels. This is considered 65F- 85F degrees and 35%-55% humidity.

Every wood or cork installation requires an expansion gap around the room perimeters as well as any vertical obstructions — pipes, door jambs, etc. The required expansion gap varies with the type of floor and the manufacturer. (Remember the installation requirements that I mentioned earlier?) I did not find expansion gaps anywhere. The entire job was installed “net” to the walls.

Each manufacturer has their own specification regarding the closeness of each joint. This is called “joint stagger”. The installer had the tile joints too close together, affecting the stability of the flooring.

The lack of acclimation, the lack of expansion joints, and the improper joint stagger, were latent installation defects. Any or all of these shortcomings could have caused a future failure. But the “wet” concrete subfloor was the immediate cause of the flooring failure.

To learn more about flooring buying, installation and care, please subscribe to this blog and check out my book, All About Carpets: Everything You Need to Know.


Who is Glenn Revere?

Glenn Revere has been a carpet expert since 1973. He’s a certified flooring inspector and the author of All About Carpets, the only book written to protect and inform you about your carpet choices, from carpet buying and carpet warranties to carpet care and maintenance. You can find him on Facebook, Google+ and Twitter.


Photos: Glenn Revere

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