Strange foundation mystery

[Bill C.]

Hi,

I noticed some water damage to the carpet and trim in the corner of a basement room that corresponds to the SE corner of the house and decided to investigate.

The house was built in '57. The foundation is essentially a simple rectangle built of cinder-blocks. The basement floor is poured concrete. The room was drywalled and the floor had trim all around so I didn't have a view of the cinder-blocks or the floor in the area of the water damage.

Pulling away the trim, I found the oddest thing: for about 5 feet along the south wall and 20 feet along the east wall, there is about a

1 inch gap between the floor and the cinder block. Also, it looks like when they poured the floor and smoothed it out they just kind of shoved the excess concrete over to edge of the floor and left it there to dry as a rough, uneven, unsightly, "lip" protruding up from the floor. This lip does not exist anywhere else in the basement, only where this gap exists. Everywhere else there is a nice smooth seam where the floor meets the cinder-block.

FURTHER, underneath the corner where the cinder-blocks intersect (and from whence the water damage seemed to be eminating) there is a cavity, probably about 6 inches deep. Shining a flashlight down the hole I could see a half inch or so of standing water. Poking around in the gap further away from the corner, I found that it was filled with pea gravel. I cannot tell how deep the fissure is or how it "bottoms out". All along the wall where this gap exists the dry wall was obviously water damaged and crumbling and needs to be replaced.

I cannot for the life of me figure out what the builders were thinking when they did this. Could there be a purpose for this gap? Drainage maybe? I'm trying to re-paint and re-carpet the room and would like to fix the water problem before I do so. It seems obvious to me that what is probably happening is that somehow water from the outside is getting in the gap and when the ground outside is very wet the cavity in the corner fills up and overflows onto the floor. One thought I had was to get some of that expanding spray foam stuff to spray in there to try and fill it up. But I worry that if this is some sort of drainage system, I might foul something up. Also, that probably wouldn't make a perfect seal everywhere and it might end up making it worse because then all I've done is make the reservoir smaller, thus causing it to overflow more often.

Anybody have any ideas?

Also, for what it's worth here are a few more clues:

1) I have big-time drainage problems in the back yard (to the east). It's probably been that way since the house was built. The problems generally don't tend to occur near the house but the soil does get very wet there too. I dug some post holes close to the house not long after some heavy rains and they kept filling up with water for a couple of days. 2) I said the foundation is a perfect rectangle. That is not completely true. On the east side there is a 2 ft section where the cinder blocks jut inward 6 inches or so into the basement. Interestingly, to the south of this point is where the gap and rough-edged floor begin. I can't tell what purpose this inward deviation might serve. There is nothing going into it (like a pipe or something) from the joists above. And I don't see any corresponding deviation or fixture on the outside of the house.

There's more but that's probably enough for now! Any help appreciated.

Thanks in advance,

Bill

[Joseph Meehan]

It sounds like standard practice to get the water that will come in and drain it away to a drywell or sump. In time these sometimes become clogged and fail or may not be enough to handle the flow.

No, well almost no, basement construction is water proof. A basement is constructed to get the water that will be there away from the foundation and to pump out any that does get through.

Fix this problem and your basement problem will be a memory of the past.

[Joseph Meehan]

It sounds like standard practice to get the water that will come in and drain it away to a drywell or sump. In time these sometimes become clogged and fail or may not be enough to handle the flow.

No, well almost no, basement construction is water proof. A basement is constructed to get the water that will be there away from the foundation and to pump out any that does get through.

Fix this problem and your basement problem will be a memory of the past.

[PJx]

Don't over analyse. They just goofed up. Regardless, I would move my drainage system to the outside. It will require trenching and drainage 360 degrees on the outside of the basement wall.

PJ

[Eric Ryder]

As others have posted, it sounds like a primitive sump/drainage setup. I didn't form a good picture - possible the slab guy used some removable form stock there to form the gap? Improving the exterior drainage semms to be the answer.

The protruding blocks (known as a HMMPH! around here in the old days - a WTF? nowadays) perhaps is the masons answer to ledge/stone protruding into the excavation?

Post some pics somewhere?

Eric

[Bill C.]

Not sure what a drywell or sump is. Are you saying what I described is (was) common building practice?

I guess the main question right now is this: is there anything I can do from the interior at this point to alleviate the problem even temporarily until I can fix the drainage problem around the house?

I live in Michigan and I won't be doing any trenching any time soon. In the meantime I'm trying to fix up the room a bit so I can move my office in there. I don't want to put new carpet down or anything until I know that, come spring the carpet won't get damaged again.

Is my foam spray idea a bad one? Will I foul something up? Would it be pointless?

Agreed. I've been putting it off because 1) it will probably be costly and 2) other than this we don't have any other water problems in the basement. And even this isn't terrible. Looking at the old carpet and trim it looks like it was probably more like a little trickle now and then that over time added up. I've never seen any out and out flooding there. It doesn't smell mildewy or anything either. Still, I'd like to fix it right.

Thanks for the help.

Bill

[Bill C.]

That's sort of what I figured. But I'm sort of trying to think of a way to at least temporarily alleviate the problem from the inside until I can fix it right on the outside. For that, I sort of need to know if it serves some purpose. If so, I don't want to do anything that will foul up the existing drainage or make the water damage worse.

In any case, thanks for the reply.

Bill

[Bill C.]

I guess I'll have to look up what a sump is. Another poster said the same thing. Agree about external drainage. As I said in another post, I'm just trying to figure out if there is anything that can be done at least temporarily from the inside.

In any case, thanks for the reply.

Bill

[Joseph Meehan]

A sump is just a place to collect excess water. It is often a hole in the basement floor with a cover and a pump in it to pump out the water as it collects. It is required my many local codes today. A drywell is generally outside and is a hole in the ground, usually with a top on it used to get rid of water by allowing it to be absorbed into the ground, hopefully away from your foundation.

That depends. If you have a sump, with pump, make sure it is functioning and that the water in that small trench flows into it. Make sure the trench is not blocked by sand, dirt etc. This will allow the water to exit the basement without causing problems.

Not only would it be pointless, but you would be sealing off the drain so it will make the situation worse. That area is the way the water should be going out, when it works and not the way it is getting in.

It is likely that putting the carpet in, caused the problem. It may have been placed to absorb water from the drain or they may have clogged the drain when they did the construction.

[PT Baker]

Did you pull the carpet back or all the way up? If you pulled it all the way up, did you see any cracking in the floor, further back away frm the wall? Does the concrete pad end at the wall, or extend underneath out to the outer edge of the wall? Is there even the slightest slope on the floor going under the wall, or is it level ?(a drain system wouldn't leave the floor level, it would have a slope). The pea gravel may be what was laid under the pad. I wouldn't try any quick or temporary fixes. I would wait until you can get the job done properly. Consider getting a foundation contractor out there just to give you an onsight analysis. It sounds to me like a screw-up. Next thing you know you'll have critters making their way in.

[PJx]

You're welcome. But I do also want to add the sometimes forgotten fact that you can rent a jackhammer to remove a section of your basement slab and fix yourself a nice sump pump area. That would hold you until you do the outside work.

Pj