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Sudden surface moisture

I'm investigating a surface moisture problem on finished concrete floor. Here are the details.....this is a perimeter room section of a larger building and this room has had an addition in the past year. The floor is about 6 inch concrete covered with a commercial grade vinyl floor tile. The building manager says that when they come in the morning the floor is wet and this started about six weeks ago. I have ruled out a plumbing or visible roof leak and the HVAC technician says the A/C is working fine. Relative humidity (air) with the A/C running is about 50% . Rain in the time period has been above normal but drainage appears good. The manager also says the problem started after the floors were freshly stripped and waxed. Right now I'm thinking surface condensation or moisture rising from the concrete added during the addition. I've not performed a probing for concrete RH yet. Expert advice appreciated.

Does the room (including the addition) have a vapor retarder underneath the slab? If it doesn’t there is an excellent chance moisture is coming up from the ground, especially with extra rain.

The building supervisor says he was told a vapor retarder was installed.

Did they take moisture tests before the vinyl was put down? what were the readings then? if they were high, then you are probably right about it being moisture raising from the concrete. you said the addition was built in the past year, do you know exactly how old the slab is?

What I’m wondering is how waxing and stripping the floor would suddenly make this start to be a problem.

This is actually pretty common in the beach areas..where surface condensation can occur if a room isn't climatized..my back patio would get so wet that my wife at first thought someone was using the shower...the humidity of the air and warmth of the air will greatly affect how much condensation occurs on the concrete, particularly if the concrete remains consistently cool..

Dew points play a big part in surface moisture issues.

Dew Point is a sneaky and nasty surprise..made worse by the fact we now have water-based adhesives and coatings..when applied to an already cool surface..tend to absorb the adhesive as it appears to be "flashing off" or evaporating. This traps a "fresh" water supply that will not stay pure in a concrete envirnment and tends to try to go into equalibrium..raising both pH AND alkalinity. High pH and high alkalinity are two terms used interchangeably, but they are NOT the same..and the reason aquaruims, pools, spas and agriculture test for both pH AND hard water (concentration), which will not necessarily correlate..and depending on the form of alkalinity are somewhat mutually exclusive...like we needed THAT confusion added!!!

Depends a lot on the surface moisture of your skin, which varies resistance all over the place.

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