My 1920s house was originally an L shape, with the chimney and coal furnace at a rear corner of the main range under the living room (think the top, inside corner of the vertical arm of the L, if looking at the house in plan view). In the 1950s, the owners added a lean-to kitchen addition by pouring a concrete slab in the space between the ell and the main range, squaring off the house. The slab is poured around the chimney and coal room. This means that the coal chute door is located about 2' under the slab along a buried old foundation wall.
The renovators appear to have sealed the coal chute door with concrete which is now leaking in rectangular pattern into the old coal room and flooding my basement every rainy season. Obviously, I'm not going to excavate under my slab to get at the door, so I assume the least expensive option is to either 1) chip out the old concrete filler from the inside and refill with some sort of expanding foam and/or 2) put a drain tile along the slab on that side of the house to keep water from getting under the slab.
Thoughts? Think I could get away with just #2? Sadly, the people who renovated the house put an impermeable patio that buts up to the back of the slab (neutral drainage) that connects with a walkway that runs parallel to the leaky side of the house and wraps around the front, leaving about 2.5" for a flower bed. I think water is getting trapped between the walkway and the house. It's gonna be an SOB to figure out how to get the drain tile under the stupid walkway. Any advice would help!
Best Answer
The best bet might be to install a French drain, i.e., a perforated pipe in gravel, set into a channel chipped out of the concrete slab nearest the house. You would not need to break up the whole slab; just to carve a channel its width. How deep it needs to be is another question; but if water has been pooling above the slab, and there's a lower place with enough slope for it to drain, then just a few cm might be sufficient.