I am having trouble finding information that would help me understand if a source of dripping water near my foundation is capable of undermining my slab. It is condensation from a gas heater that has been piped out of my basement. It amounts to @ 5 gallons per day, and is dripping a few inches from the edge of our foundation. We have noticed settling in our house, and I wonder if it can be attributed to this. The house is old, and heavy, and three stories tall. I am a door expert, but know nothing about soil erosion etc.
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Replies
It doesn't seem likely to me
I'd be more inclined to suspect less-than-ideal slab prep (poured partly on topsoil or uncompacted fill), and/or some other source of water that's washing out the fill. I might try to pipe that condensate drain away from the house but it doesn't seem like enough water to do harm, especially assuming that the heater is fairly recent.
pipe it away.
It is easiest enough to do. Really, you never want a constant source of moisture right at your foundation/footing - although yours sounds fairly minimal. As far as how much the water has effected your situation, there is no telling from here as it all depends on your soil type.
If you want to get and idea how much the water source has effected the soil get a soil probe rod and stick it in to the suspect area. If it is mushy, you will be able to drive the rod in up to the handle with just your arm strength. http://www.google.com/products/catalog?hl=en&q=soil+probe&cid=2239846305601780967&ei=5s4GTM3fPJOEwQXUtqnPCQ&sa=title&ved=0CAcQ8wIwADgA#p
I'm guessing you probably don't have a soil probe so a piece of rebar with a handle made of a 12" 2x4 with a hole in it to accept the repar will surfice.
While that much dripping against the foundation isn't a great thing, it's very doubtful that it could cause any significant subsidence.
I am curious, though, how you can have 3 stories and a basement on a "slab", and how condensation from a heater (furnace?) in the basement drips outside.
Also, where do you live? It'll give us a clue as to how deep the foundation would likely be.
3 stories on a slab
I live in the Pacific northwest, on a hill, so I have a daylight basement, with two stories above it. The soil is expansive clay, and the house is85 years old. We are going to re-run the condensate line to a gutter drain, so that part is solved, but I was curious to get opinions about whether the 3-5 gallons dispersed near the foundation could account for the settling we have noticed after the heater was put in last year.
House is 85 years old and 3-5 gallons a day has caused the foundation to subside in a year?? Must not rain much up there in the Pac NW, eh?