Questions about the possibility of increasing the grade on the soil just right around my external walls

Question

My house is about a hundred years old. I replaced the roof and gutters about eight months ago.

When it rains very heavily, we get some water in the basement, in three tiny streams from three of the corners to the central drain. I have had several contractors over to make recommendations and have come to realize, they are (obviously) sales people interested (of course) in selling their own product. I have no idea what to believe concerning what is actually needed and actually best given what I'm seeing.

All these contractors recommended internal drainage, because that's what they sell. I'm reading in some places online that I should first make sure the grading on my yard is good, as well as the length of the drain pipes on my roof gutter system.

Lengthening drain pipes was easy of course. I'm now looking at the slope on my yard.

In general, over the yard as a whole, the grading is good--in general, everything slopes away from the house. BUT in many places right up against the house, there is basically a downslope towards the house. As in, just a foot or so right next to the house has, not as deep as a "trench", but just a slight downward slope toward the house.

So what I'd love to hear, is that can just dig up the plantlife (grass etc) right there at the wall, and get clay soil and basically pour a small layer of it all around the house, pack that in, then replant over it. Basically "patching" the grade so to speak.

Is it plausible that this would actually have a net positive effect on how much water gets down into the soil around the foundation, large enough to make the procedure worth it?

On one side of my house I just have like four feet of yard before it hits a fence dividing my yard from my neighbor's yard. That side of the house also is where the worst basement moisture problems happen. It also is a bit of a jungle so needs considerable clearing before I can be sure what the soil grade is like over there. But I am assuming that once I clear it, if it needs regrading whether as I've described above or more majorly, it will not be cool to just have all the water flow into my neighbor's yard. What do people do in cases like this? Is it plausibly DIY for someone who hasn't really done anything like this before? Or do I need to hire somebody? If the latter, how do I know whether they're doing what's actually needed and best and not just trying to sell me whatever it is they typically try to sell people?

I don't believe I'll be able to actually waterproof the foundation externally as I'm not convinced it's safe to do that kind of large scale soil shifting given the age of the home and the fact that the foundation does already have horizontal cracking and slight bowing on the three walls where moisture does get in.

Similarly, if I'm understanding right, any substantial external drainage system would involve something similarly invasive happening so I'm not so sure whether it's a good idea.

But all thoughts about this are welcome.

Including some pictures from all around the house below.

Answer 1

Instead of inviting salesmen, get a structural engineer or architect with the experience and work out what needs doing.

Look at the slopes and also if there are underground springs, poor drainage or just a high water level to deal with.

Answer 2

I would not particularly seek out clay, but yes, you can fill next to the house, which often settles because it was dug up to put the foundation in, and filled, and then settled over a winter or two (or 102, but mostly the first one or two) and was not re-filled to maintain the grade.

Limit the extent to which you dig out, unless you are willing to come back in another year and re-fill on top after what you dug up re-settles. It's very difficult to mechanically compact to the extent that going through a couple of freeze-thaw cycles will, so it's generally easier to just let winter work for you, if you can allow it the time.

If you do dig out much, you can set an impervious later (such as XPS foam) at an angle away from the house underground, before filling on top, as an "underground roof" to move percolating water away from the house. But that's going beyond the basics of just making sure the surface grade is correct.

All you need to set surface grades away from the house is a straight board, a 4-foot level, and a 1/2" block for one end (the one away from the house) of the level. On the side with the short distance to the neighbor, slope out and then front or back (or both) depending where your water is to end up.

Answer 3

Moisture is either coming up from below (a rising water table) or its coming from the surrounding ground water in the saturated soil, or both.

If it comes up from a rising water table, it will enter the living space from below through the crack between the foundation wall and slab.

If it comes from the surrounding ground water, it COULD enter the living space through the wall, especially if the EXTERIOR side of the foundation wall is not sealed properly.

Either way the moisture enters the living space it will need to be collected and disposed. I think the best way to collect it is on the exterior side of the foundation wall in drainrock and a perf pipe laid 6”-8” below the interior basement slab.

To keep the subsurface water from seeping through the wall, I recommend installing a moisture barrier on the exterior side of the foundation wall and install a 2” thick plastic mesh on the wall to allow water to flow down to the perf pipe. (If dirt is allowed to be backfilled against the wall, the dirt could hold the moisture giving it a chance to seep through the wall.)

Once collected it needs to be disposed by extending a solid pipe over an embankment or in a collection well and pumped away.

This may be the most expensive method of solving the problem, but it’s sure to work.