Basement remodelling - moisture questions

I am in the process of remodelling our basement. Our home is about 2 yrs old. I did not think that I had a moisture problem, except that on occasion, leaves would plug up the footing drain in a window well and water would come in the window. So I am going to address this issue outside. However, after reading many of the threads on this site, I am wondering about other issues.
A little background. I have a single-story home with a full basement (about 2300 sq ft) with 9ft ceilings. About 6-8 in of the foundation walls are exposed on the outside. The walls are poured and have a spray-on coating on the outside. I have 1 larger crack (2-3mm wide) across the whole floor that has been there since it was poured, and I have recently filled that in and painted waterproofing paint over it as well as many of the other much smaller cracks. There were some hairline cracks in the walls stemming from two of the windows and I have sealed them as well. All of this was a precaution. I have never had moisture through any of these.
I keep a dehumidifier running to keep it at 60% humidity, and it runs much of the year. It can collect 45 pints in a couple days in the summer at peak humid times. I don't know if this is abnormal or not, but there are no return vents on the 92% efficient furnace/AC in the basement, and that could contribute. Any thoughts would be appreciated on this.
Here is the issue. We have a 12x20 area with carpet remnant layed over 6mil poly. When we started moving things around to build the walls, I noticed that the concrete under this sheeting is darker than the rest of the floor. After pulling a section back for a while, the color has lightened. There is no actual condensation under it, and it has been in place for about 2 yrs. After reading some messages and my DIY books, I am somewhat concerned.
I have asked my builder about this, and he did not think there was any problem. The floor is 4 in thick concrete with pea gravel from the bottom to the top of the footings and there is drainage tile around the outside and inside perimeter of the footing leading to a sump pump. The pump runs normally a few times a day, rain or shine.
Should I be concerned with this issue? Do I need to waterproof the whole floor to prevent moisture? I can't imagine that there is that much moisture under the floor with the drainage available under the floor. Could something not be working properly? Please help, as we are in the process of framing, and don't want to go too much further if there is something that needs addressing.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
<snip>
Sounds a lot like my basement. It's finished with 6" fiberglass, vapor barrier, drywall. It's carpeted with commercial type carpet glued down. With the summer humidity, I can not put anything like say plastic/cardboard boxes directly on the floor else there will be condensation underneath ... the floor is cool and apart from insulating, that's just the way it is. When the new furnace went in, I had a cold air intake installed to draw at floor level which helps ventilate the basement in summer (reduce the humidity, stale air), and it helps pull the cold air off the floor in winter. And that's it.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I had the same situation. If there is moisture under the floor, the vapor will find its way up through the concrete. I painted the concrete with a sealer -and- used those 2x2 dricore panels from HD as the sub-floor. It wasn't cheap, but the floor is warm and the air spaces give the concrete some breathing space (I know that sounds stupid but I don't know how to explain it)

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.