what is the best way to stop a leak in the basement (where the concrete slab meets the wall along the base? I?

Question

I have already rerouted the downspout from the gutter away from the house

Answer 1

Great first step. Also check to see that the soil around your house is graded away from it. No point in wasting time and money trying to seal a leak without at least reducing some of the water pressure/or sources behind the wall. Is the leak near your sewer pipe? (Sometimes you can tell by the smell of the water.)

Also, if you have a sump pump, is it deep enough? The water should be pumped such that it never is high enough to touch the floor slab.

If you are on a hill you may need to swale the runoff from above you around your house.

Lastly, clean the crack as best you can. Seal it with a flexible caulk as the slab will move independently from the wall.

Answer 2

Make sure that the gutter drains at least 3 feet away from the house and also make sure that the ground is built up so the soil slopes away from the house. If you have to get some dirt and pile it up there, anything to redirect the water away from the foundation.

Answer 3

Hydraulic cement.

It will cure directly over a leak. Thats right, even if you still see flowing water. Many companys make such a product, but i tend to see the UGL brand the most.

Also check the pitch of your property, around your house. And make sure the slopes are away, and not towards your foundation.