In one corner of my basement, after a few heavy rains, I see a darkening of the concrete floor. To touch, the concrete feels damp-ish. I say damp-ish, because when I pull my hand away, I don't see any moisture on it. There is also no beaded moisture on the surface.
The house is 57 years old, so I don't know if there is any drainage tile on the outside of the foundation.
Since the house is so old, it has settled and the surrounding landscape slopes towards the house - about 20' away has a 2-3 inch slope towards the house.
I believe the moisture is wicking up from the ground water, as there are no cracks in the foundation floor or basement walls.
Multi-part question here:
Will backfilling and building a slope away from the house stop this or at least greatly reduce the problem? Or is this simply a matter of the water table being higher than the basement floor? I'll re-iterate that this problem is only in one corner of the house.
I've only owned the house for 3 years, but it looks like this has been an issue for a number of years, with little real problems. Is this something I really need to worry about, or is it mostly cosmetic? The idea of "moisture in the basement" is typically a red flag, but since there's no beaded moisture, it's only in 1 corner, and there's no cracking on either the floor or walls, I'm wondering if this isn't a big deal.
Should I bother to get a dehumidifier or sealant for the concrete? Is that typically what is done in this situation or will that just be a bandaid to a deeper problem with the concrete/fill under the basement floor?
Edit: Not sure if this is relevant, but this section of floor also has a drain pipe connected to, I'm guessing, the sewer. My washing machine drains to it, but I don't notice any correlation between washing & discolouration.