Higher air RH + not fully dried concrete + cool concrete + little or no air circulation
The right angle junction of the wall/floor creates a dead air pocket (since air moves not in right angles but gentle curves/swoops) thus the air does not bring heat and drier air into the junction leading to a dew point situation (microclimate).
Last summer, got called to a home with similar “problem” by a local franchisor* of a pre-manufactured home company. His clients had just moved here from New Hampshire or Vermont (Tired of Mr. Shrub; the gent was ex forces) They were sure thay had a leak in the basement corner where the well system pressure tank was located. The vendor had already dug up the exterior corner to check the drain tiles- no problem (He should have called me first; would have saved the $$$$ from digging up a new foundation)
I told them it was a localized microclimate from the coolness of well water in the tank and the tank being in a basement corner allowing no natural air circulation into the corner. I said more heat in the area plus a fan to circulate air and a dehumidifier should cure the problem…it was not a leak!! When I said this, the lady walked out of the room and would not speak to me again on site. This was on a late Friday afternoon…On Monday morning the gent drove into the vendor’s yard (on his $30-35,000 Harley) and said the moisture was gone!!!
*(It was a bit funny as he had talked to me in 1986/7 about becoming an associate HI with us in another city…then he became a home builder/vendor)
My $.02
The builder knows what it is, whatever it is. He wont let you take pictures, Prehaps hes just covering his butt, but that does sound silly. Ask the client to take them.
There are a number of products that will damp proof the INSIDE of a poured wall. buy a quart and a do a section. If you get the clear stuff, no one has to know.
This is all hearsay from the buyer but he told me 6 dehumidfiers before installing the drywall and carpeting (they had to wait another day before installing the carpeting due to the amount of moisture on the basement floor), then the running of the central air.
I’ve been in a lot of basement during new construction over the years and never seen it close to what was described or what I had seen during the home inspection (especally when the house as been closed up for as long as it has) so I’m having a hard time with the high humidity thinking. Moisture has to be coming from somewhere and all of it from the warmer air from the first floor or a combination from the air from the first floor and concrete is hard for me to beleive.
Walls and floors are covered up at this time so getting the humidity out of the basement is going to be much harder.
Ya see- that’s just the thing. When starting this thread, I was not really asking for help diagnosing the problem. Leaks, concrete out-gassing, micro environment… what ever. I think the liquid water standing at every wall / floor intersection is not acceptable.
