Here is what I did: - I first tested the concrete floor for moisture evaporation by taping 2ft x 2ft sections of thin plastic (e.g., polyethylene, plastic painters tarp, etc) over the concrete, ensuring a air-tight seal is made around the perimeter of the plastic sheet. Did this in several different areas of the concrete slab. Left the sheets in place for 24 hours or so, and did not observe any moisture evaporation (i.e., non trapped under the plastic). If you have moisture trapped under the plastic, then the following procedure may not be the best solution for your basement. Also, if your basement is prone to flooding, FORGET H/W FLOORS! - After completing/passing the moisture test, painted entire concrete slab with concrete sealer (Behr 1-Part Epoxy Acrylic Concrete & Garage Floor Paint, available at Home Depot). - After sealer has dried for a couple of days, proceeded to lay a foundation of 1 x 4 treated lumber laid out flat (on 4" side) in a 2 x 2 grid that will need to be glued to the floor using ample amounts of construction adhesive. (NOTE: The treated lumber is used just in case any moisture finds its way through the concrete sealer, and the lumber will not rot if this happens. Keep in mind that even if the above moisture test passed, and a sealer was applied, cracks can still appear in the slab over time, and moisture can find its way through these cracks.) The grid will need to accommodate ¾" x 4 x 8 sheets of sub flooring. With the 1 x 4Âs are laid flat, the 2 x 2 grid is stronger than having the standard 16" on-center spacing using for the joist of most residential floor systems. I used the grid layout for additional strength to support items such as a pool table, etc. Be sure to leave at least ¼" gaps (for expansion) between ends of wood sections and around the perimeter of the room and room walls. If your concrete floor is uneven, you will need to either shim the 1 x 4Âs to make them level or use a floor leveling product to make the concrete slab level. I used stacked bricks to hold down boards that were slightly crooked until the constructive adhesive dried (over night). This will help you keep the floor reasonably level, assuming the concrete surface underneath is reasonably level. - Next step is to add your 2nd layer of moisture protection, 6 mil polyethylene sheeting, which can be stapled on top of the 1 x 4 lumber. Ensure you overlap the edges by 4 to 6 inches and that the overlap sections are stapled onto a 1 x 4. - Next step is to add 3/4" sub-flooring. I used the Advantage tongue and groove product sold by Home Depot. This stuff is better than layered plywood and other OSB type products I have seen. It costs a little more, but it simply stands up to moisture better and appears to be stronger than the alternatives. I used 1 ¼ inch decking or galvanized screws to secure the Advantage to the 1 x 4Âs. - On top of the above, I installed Alloc laminated flooring, which is a floating floor that is much better than the stuff sold at Home Depot and Lowes. It is easy to install compared to hardwood floors, and in my opinion is much more durable. Just Google "Alloc" to find a dealer near you. - All of the above may seem extreme, but I feel 100% confident that no moisture is going to make it through the concrete and into the laminated flooring. The floor is very study, does not give, and is quieter than my ¾ inch Brazilian Cherry flooring installed on the main floor above.

I had a similar sort of experience recently, except my house is fairly new and my family and I are the only people that lived in the house. I think it was somewhere around 3 am, I was in the living room watching youtube. I heard some sort of chopsticks-sounding object fall onto the kitchen floor. I didn't think much of it and went to check what it was. I was on my way to the kitchen, when I was nearly there, music starts playing from the room right next to the kitchen. It didn't seem like it was coming from outside. It gave this ominous, backrooms type of vibe. I knew for a fact that there was nobody but me, downstairs. I froze and wasn't able to move at all for a few seconds. Being too scared, I didn't check it out. I turned around, went back into the living room, and continue the video I was watching. After 20-30 mins later, I was curious. I gathered enough courage to go back into the kitchen to check what made the noise and what the music was all about and so I did. I was walking around the kitchen and to my surprise, I didn't find a single thing on the floor that could have made a noise when dropped. I even checked twice to see if I missed anything, but still couldn't find a single thing on the floor. At this point, I was feeling anxious. I walked into the room where the music was playing, but also couldn't find any source from which music could have been played. I don't know if I was hallucinating or not. I didn't want to find out, so I just went to bed. crazy night

First off, thank you for the advice. I decided that you are 100% correct and I shouldn't pre-judge what has happened. With that in mind, it has now been about 3 weeks since they came out the first time and inspected the floors. About two weeks ago, they had a more "senior" flooring person come out to do another inspections. I gave them about one week to review the matter and called them for a status update. They never returned my called. Since then, they have been largely uncommunicative with me. I've been calling every couple of days asking for a status and get no return calls. While I am upset, I've decided that keeping things calm and non-aggressive. The lack of calling me back is not giving me a warm fuzzy. I'm going to continue to call them for then next two weeks. Hopefully they contact me back and we can work through this. If not, I'll have to decide what my next steps are. Last week, our neighbors who have a similar house as ours (built in 1956) had floors put in. I asked if I could see how it was coming along and they let me in. I noticed they were having a barrier put in between the floors and the slab. When I inquired the person installing the floor about the barrier, he stated "it's to reduce noise and also serves as a moisture barrier". I'm going to call the nwfa.org and have a inspection done. Thank your advice. If you have any more advice, I am all ears.

Thanks SJ and Springtime Builders. We did not have a basement waterproofing expert on hand. Definitely should have done this before starting to finish the basement! The house had been gutted, including the basement. We had basically exposed concrete floors and walls (foundation). No visible cracks. The walls (old and new) were insulated before the drywall was placed. Our contractor thinks this is a condensation issue. While he does think there are drainage issues under this very old house, he thinks addressing this would involve tearing out the concrete floor and digging several feet further to install a drainage system and would be extremely expensive. He does not think we have a crack/leak in the slab or foundation. He has advised that we install this: https://www.wavehomesolutions.com/wave-moisture-control-basement-unit/ Of note, as the house is nowhere near being completed, none of our HVAC components are up and running yet, so there's no air circulating in the house at all. Perhaps once the house is powered up (and with the addition of this ventilating/circulating unit), the moisture issue will improve? Is there a reliable way to test if we are dealing with condensation vs seepage from a porous slab? We are not currently living in the house and are not on-site regularly. I will try to take some photos, especially if there are active moisture issues when I am there. Thanks again to all!