Moisture in slab before carpet

[ALinCarolina]

This is not a garage or workshop issue but probably more experts here than anywhere else. I have a rental house where we had a sewage backup onto a bedroom with carpet on a slab. Had to have all carpet removed and area sanitized. Have had a dehumidifier running since it happened about 10 weeks ago. Two weeks went to Lowes to start process to replace carpet. Their contractor came out but said the moisture levels per his meter were still too high, 32%. I talked to Wagner meters and they said that figure is questionable and that measurement could only be used for comparison to other areas.
I ordered 3 calcium chloride tests. Placed one on the area near bathroom where flood happened and one on other side of room that stayed dry. Then one out in garage as comparison. The garage and the dry side of room scored less than 1 lb per 1000 sqft/24 hrs MVER. The area flooded showed 5.2

I have seen anywhere from 3 to 5 as acceptable depending on the source. I'm afraid Lowes installers will still say the moisture is too high so was considering applying a moisture sealer. I read impressive claims for instance about Ghostshield's Vapor-Tek 440 epoxy that it could block up to 20 MVER. It is quite expensive and all I can find is the 3 gallon kit. Lowes used to carry the 1.5 gallon but not available. The room is only 150 sq ft and the area that is in question is smaller than that.

I plan on selling this house this spring so didn't want to invest anymore than I have to. Is there something different or special about the Vapor-Tek 440 epoxy? I see other sealers/densifiers but not sure what level of sealer I would need. Any help or advice is appreciated.

 

[BombShelter]

Not enough information, is this a basement or slab on grade, I'm assuming there's no basement? What is the outside humdity/temperature? How much water is the humidifier pulling out, are there open doors or windows in the room?

The water can be coming from the air (ambient) or from underneath the slab, pushing up. A cold slab will collect surface water when the outside temperature starts going up. It's going to be in the 40's today here, if I open my garage door, all my metal parts will be sweating by the end of the day.

Moisture meters can be like snake oil, depending on the user; I use a high-end GE Aquant Protimeter with non-contact pins, but it does have to be touching the surface. It goes up to 999, I consider concrete at 200 to be dry (I never see it going much less than this). Drywall will not get a reading as long as it's not wet. The Wagner Meter looks like it's for professionals as well, if that's what Lowes recommends, I'd go with it and find out where the moisture is coming from.

Carpet might not be the best material, or find a brand that's for higher humidity areas. If the concrete is too wet, the surface coatings might not stick or flake off in the near future. Some of my cabin friends swear by the new plastic waterproof fake wood floors, they snap in place.

 

[ALinCarolina]

The house is in mid North Carolina. Here is winter the air is much drier than in summer. Slab on grade, heat is on in the house. The humidifier is draining some water but not able to measure since it is piped to a shower drain in the bathroom. I know where the water is coming from. The sewer backup flooded that area of the bedroom. That is the only area of the room that is showing any moisture. The other end of the room and the unheated garage are dry, no measurable moisture with the calcium chloride. We've owned the house for 15 years and the carpet has been fine until the flood.
I have 3 moisture meters. One is a Wagner, it is inductive with no pins but designed for wood. It is not the C555 or C575 used for concrete. But even the C555 only measures up to 6% and costs $475 new. I tried all 3 of my meters and got mixed results comparing the bedroom to the garage. Hence I ordered the calcium chloride.
I have waited for 10 weeks and thought it should be drier by now so that is why I am considering some sort of moisture blocker. According to the Wager support person the 32% the installer measured is at least suspect and not accurate.
Another surprise is I thought that is there is a moisture problem I should just go with vinyl but the installer said that vinyl requires down to 6% moisture while carpet only requires down to 20% (by his measurements). That was backward to my assumption but I guess the carpet "breathes". the Wagner guy also said carpet would be a better choice with moisture present.

 

[ALinCarolina]

Update: The flooring company said that the floor is dry enough at 5 MVER and they installed carpet today. Will see how things go but will probably sell the rental house this year anyway.