Moisture is leaking through my basement walls, but the house is surrounded by concrete. Worth fixing?

Question

I'm in Minneapolis, in a house built in 1886, fully renovated a few years ago. The basement is finished. This has been an extremely wet winter, with lots of snow and ice that is now melting.

Some guests pointed out a damp patch of carpet in the basement. When I pulled it up, it looks like water is leaking in through an exterior wall. I can't see more without taking off the drywall.

The basement has leaked only once previously, but that was due to a blocked sewer clean-out pipe, and that is not the cause this time.

The house is surrounded an all sides by sidewalk. It is graded/angled to allow for drainage. The house has gutters, but they are completely blocked with ice. I suspect that the leak is related to the build-up of ice on the sidewalk.

I am deciding between these options:

1. Pay a contractor to come in and investigate. Because there is sidewalk on the exterior, I expect any repairs will be very expensive.

2. Just fix the damage, and in the future try to be more diligent about keeping the sidewalk clear of ice.

What are your thoughts?

Answer 1

Did you ever resolve this? Did you figure out the issue and fix it?

An 1886 basement is probably constructed from natural stone. Is it? Is there any unfinished exterior wall in the basement that you can see? The stone itself is porous and the pointing, unless it has been redone recently, is also usually leaky in a basement this age.

In heavy rain, or during snowmelt, the walls will leak into the basement. You can improve this by ensuring the gutters drain far from the house but if it's surrounded by sidewalk that's difficult, and you cannot fully stop the water from penetrating the walls after heavy rain or snowmelt.

If the basement was finished and decorated without regard to the exterior wall construction you will need to rip down walls that are against the exterior. Some things you can do to improve this:

• VERIFY the water is only coming through the walls. Sometimes it comes up through the concrete floor. If that is happening you need to rebuild the floor, and I don't know the details. This is usually only if you are in a low, frequently flooded or swampy area.
• [ Bad idea ] Trench the exterior and seal the walls from the outside. This is a bad idea with an old, natural stone basement because it can turn your house into a boat, which it was not designed to be. The basement walls might not react well to built up water pressure from the outside. Better to let the water sieve through as it has for 5 generations. Your sidewalks make trenching an even worse idea due to the expense.
• [ Good idea ] Install a french drain along the inside, sump pits and sump pump around the entire perimeter of your basement. Rebuild the interior walls that face the stone, with a vapor barrier against the rear of the interior walls, and do not attach them directly to the outside walls. You are essentially building a room within the basement isolated from it and impervious to moisture, with a drain all around it to collect the water between the walls.
• [ HELPFUL ] Install a continuous dehumidifier and maintain it. They need a lot of maintenance, and replacement every so often. The french drain and proper interior walls will prevent large amounts of water from entering the decorated space but there will still be humidity during floods.

Answer 2

I would get the ice away from the walls by a yard or so to try and minimize the incoming.

Drying out the damage is next - perhaps a dehumidifier...

Could you consider a drastic (and expensive probably) solution - by excavating down each outside wall and putting a treatment to seal the wall, also uses a plastic membrane (the one we had to use has "hats or thimbles" molded into it to make it 1/2" thick to allow the water to drain.

You could also consider adding a layer of insulation to the wall at the same time if appropriate...

Answer 3

I would clear the ice and dry the area out fans circulating air work quite well in the winter because humidity levels are low. A dehumidifier could further speed the drying. Since it has not been a problem in the past I would probably just do as you said and keep the sidewalks clear, but probably would not invest a lot unless this becomes a regular problem.

Answer 4

The issue likely is hydrostatic water pressure on the outside of your foundation, basically the water level in the soil is higher than your footing and pushing in through the wall or even under the slab. This is normally prevented by a footing drain just above the footing that has holes in it to gather the water and then drains somewhere away from the house. Being that your house is so old, it's likely that it does not have this drain or it has been clogged or otherwise compromised.

I doubt that it has anything to do with the ice but rather just the normal melting of snow and ice turning into water that goes into the soil and flows like a wet sponge.

Yes, it's expensive to fix especially since you have the sidewalk. Thinking outside the box here, you might be able to do a drain a bit away from your footing to intercept the water before it gets to your home, and this would just be a ditch and would not require replacing your sidewalk. I would talk to an civil engineer first though to see what they think of the idea.

Otherwise, it will happen each time you have similar winters. You can just live with it and dry things out. Perhaps set up your flooring so that it is not damaged by being wet.