If you decrease surface water will groundwater decrease or stay stagnant
Hammer| Posted inGeneral Questionson
So I already asked previous questions about a basement dampness issue but now have questions about ground water. So basically I have gutters dispelling water away from foundation and I’m going to slope dirt away from foundation so surface water can be channeled out through a French drain and sloped sidewalk. Using 6 mil poly covered with dirt and gravel. Is it possible I will still have basement dampness coming through floor if there is no surface water coming down. Does ground water just sit on surface in one area. I have a backyard that is lower than foundation and it’s not a swamp. There are no lakes near me or any body of water underneath me.
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You might find this helpful:https://www.usgs.gov/faqs/how-can-i-find-depth-water-table-a-specific-location?qt-news_science_products=0#qt-news_science_products
Your question could quickly become complicated, but for the purposes of building design, you want to foremost divert surface water away from your structure (you seem to be on top of that). In some locations, the water table may never reach heights of concern. In others, in most certainly will. It's very site specific. But either way, it's a good idea to provide capillary breaks between inside materials and the ground, which will almost certainly have some level of moisture. This means a layer of crushed stone under your slab and also 6mil or thicker poly (vapor barrier) will help keep the basement floor dry.
If there is concern with groundwater, this is usually managed with drainage strategies at the lowest elevation of the structure on the exterior: around the footing. This typically involves crushed stone (well draining aggregate), geotextile fabric (to keep the fines out and retain its draining properties), and perforated pipe to daylight or sump pump (to provide low resistance path for water to exit).
>"I have a backyard that is lower than foundation and it’s not a swamp."
Keep in mind groundwater doesn't level off like a lake. It will contour to landscape some. If the low-spot in this 'backyard' is very near your foundation, it may be a good indicator, but the farther it gets the less reliable that would be.
> Is it possible I will still have basement dampness coming through floor
一定数量的水来自as vapor from damp (not wet) soil. Blocking or drying away this moisture can be important.