help with water seepage under slab...

[woodgeek]

I live in a 60s era 'side-by'side' split level on a steep hill. The front of the house is like a multi-level slab-on-grade (grade below the lowest floor line) the back looks like a full basement (grade 6-8' higher than the floor). I have french drain/sumps in the back, which is a story for another day.

I have a frustrating problem on the front, walkout part of my house--I get flooding at the lowest point, which is my front-door/foyer area. I **think** the water is coming from the front of my house, b/c it is exacerbated by overflowing gutters on the front, and winds driving rain against the front of the house. I think surface water is seeping under my slab and reappearing at the lowest point in the multi-level slab. I have found a few areas with what look like 'snake-holes', where I think the ground subsided under the slab and water dug a tunnel. I need to do a garden hose test on those--see if I can get water in my foyer just by dumping water in those holes, etc.

The question is: if I'm right, how do I fix it....is there a setting, water repellent material I can just tamp in there? Do I need to excavate down and repack the area? Should I make a buried 'skirt' of some membrane to carry ground water away from the slab?

Note that the landscaping is already steep graded downslope away from the house--I think the water just sees a more downslope, subterranean path under my house.

 

[smokinj]

What shape is your gutters in and how far are the away from the house? Your on the right track best you can do is follow the water.

 

[woodgeek]

My gutters were recently replaced, and work well in all but the most intense downpours. What I didn't mention, the builder must've loved concrete--the whole front of the house is concrete--entry steps, lateral steps, a sidewalk to a concrete patio, all butted right to the slab. I think the water sheets along that stuff (perhaps aided by flooded gutters), and then flows backward under the edge to eventually snake under my slab. I should say I have found snake-holes along the outermost edge of that concrete-work. The line b/w the concrete-work and the slab is carefully sealed along the whole length.

 

[semipro]

I'm not sure exactly your situation but it sounds like the only option is going to be installation of subsurface intercept drains to draw off encroaching water. It sounds like this could be a pain with that much concrete around.

I seriously doubt that filling in holes in the soil is going to fix this though it may slow it down some.