Solid Hardwood, Engineered and Laminate Flooring - Laminate floor swelled up – no leaks

The laminate floor in the condo I rent swelled up (parts of the panels became thicker) in various places all over the living room. The problem started at the beginning of July and there has been no new swelling since the end of August. June and July in Toronto were unusually rainy and humid this year. We had no water leaks and we use a vacuum cleaner to keep the floor clean. The laminate floor was installed around two years ago after a water leak destroyed the previous floor. Apparently the concrete was professionally dried before the installation.

Has anybody heard about causes for such swelling up?

My landlord claims that I must have spilled something on the floor to cause the damage and wants me to pay for the replacement of the entire floor.

A leak from two years ago on concrete that you state was 'professionally dried' and laminate that did not present 'swelling' until now has something else going on. No leaks. Have not mopped the floor in two years and vacuumed only.

One possibility if house is built on slab that rising water table due to unusual heavy rain could have entered the slab. This should be evidenced by swelling occurring over majority of floor or in various locations as you indicate.

You state the problem was confined to the livingroom. Leaks can be sneaky. If stopped up gutters and downspouts and water enters walls, swelling would be seen along walls. Windows and doors that do not properly close and seal would cause moisture penetration and swelling in floor in primarily in those locations, but water tends to follow the path of least resistance.

You mention high humidity. If humidity is not maintained at 35-55% year round and temp around 70 degrees, then humidity could be an issue.

Failure to install vapor retarder beneath the laminate flooring would allow vapor emissions through concrete and cause swelling. If you have had no problems with the floor until the recent unusually heavy rain and humidity, then this could be another possibility.

Thanks twelvepole.

Two more pieces of info:
I live on 18th floor of a high-rise building and between windows and living room there is a solarium with laminate floor without any damage.

After reading a few of threads on the net I developed a theory:
During the summer I was using AC quite extensively. This means that the air near the floor was quite cool. On the other hand the air near the ceiling in the apartment below must have been quite warm. This might have created a situation where the air below the laminate floor was much warmer than the air above it, creating good conditions for forming moisture underneath the laminate.
Does this theory make any sense? Did it happen to anybody this way?

Yes, that does, to an extent. Dew points are funny things, and no one thinks about it. Concrete should have a moisture barrier over it before the laminate are installed, not just a cushion. People think since they are up on the 18th floor, there is no concerns with concrete moisture, but there is! All you have to do, is have the windows open, or go out of town and turn you HVAC off, and it will gain moisture and possible dew points acheived on the concrete. It may not happen all over the floor, either. Around AC ducting and vents can cause the concrete floor in your apartment be below dew point temperature.

First thing to do would have a plank removed to varify a moisture barrier was used. A certified flooring failure inspector is needed. One that can take up a plank and put it back in, after he records his findings.

If you can locate a long section of wall area with no door near on the lond side of the flooring, you can pull the qtr round off and unsnap a section yourself to see if a poly film exists on the pad or a plastic moisture barrier was used with the pad,
Note: moisture barrier must be between floor and pad, or will cause condensation at the floor pad interface.
all this can be done with out the hiring of an inspector, then dependent on what you find decide on the inspector to help defend yourself.

and you don't need a vapor barrier at all if the moisture level is low enough, per most manufacturers instructions.

If it is over concrete, yes you do require a moisture barrier, under a floating laminate floor. Dew points and concrete, that is where we have gone in the conversation, Hot Oakie.