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Rat slab

5.5K views 87 replies 6 participants last post by  A. Danger Powers  
#1 ·
I searched around but couldn’t find an answer. My basement floor is mud covered by black plastic. I’ve been reading about rat slabs and how they can control water. I have water deep down in the mud. I can make a hole and water will slowly fill it up. Would covering it with a rat slab help?
 
#17 ·
I think @Nealtw is giving you some great direction. A couple items I have run into that could help that are relatively easy fixes are checking the soil grade around the foundation and checking downspout length/location.

We use to have water issues every time it rained. We started removing rock from around the house and there was ~35 foot long stretch where the soil grade went towards the house. The previous owner just filled the rock to make the grade seem correct. We brought inn ~10 cubic yards of fill dirt to correct the grade 14 years ago and have had 1 instance of water issues after 7 days of record rain.

The other item is making sure all your downspouts are depositing water far enough from the foundation. Several of my neighbors had to go 10+ foot out to keep the water from pooling against the foundation. It has to do with disturbed soil that was not properly compacted draining water towards the foundation rather than away from it. Once the downspouts clear the disturbed soil, it flows away from the foundation.

Hopefully there is a cheaper solution but agree with everything @Nealtw is suggesting.
 
#19 ·
Sorry, I missed the part about the parking area grade. Fixing that should definitely be part of the remediation.

My in-laws had a similar issue, they ended up having to do a slight V on the driveway with a grated trench drain/channel drain running across the driveway (parallel to the house) about 3-4 foot from the foundation. It dumped into a ravine ~10' past the house and eliminated 90% of water near the foundation. The less water the foundation drainage system has to deal with, the better it will work.
 
#21 ·
The drain would be surface level but graded on both sides. You can do custom, custom order, or off-the-shelf. Theirs was custom order since it was so long. Here's some internet pics to give you an idea:

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The above would not replace the foundation drainage but augment it.

Since your foundation is acting as a dam, it doesn't take much rain to create a large amount of water in your basement. At 1 inch of rain, a 1,000 square foot area receives 600 gallons of water.

I'm in a dry climate so a big summer rainstorm is ~1/4 inch. That equates to ~540 gallons of water deposited within the immediate drainage footprint of my house (house area + 10 feet out from foundations). I know this is fairly accurate because I have 6 @ 55 gallon rain barrels on my downspouts and they fill & overflow with one of these rains.

As far as how much of that water soaks into the ground... You said the water in your basement rises when it rains. Water follows the the easiest path which right now is against your foundation & into your basement. Grading & drainage will change that so the easiest path is away from the foundation. Grade causes water to go out out before it goes down...
 
#22 ·
As I’ve said before, I don’t think there was ever any drain of any kind on the bowing wall side. I can’t imagine why they didn’t put one in when it was built.
I always though the water rose in the basement because the water table was high but now I’m seeing that’s not the case. Water has been getting under the wall for over thirty years. It’s wet all the way to the other side of the basement. Our house is almost in a bowl. The basement floor is lower than the ground outside by a few inches.
 
#43 ·
Interior drains are installed to collect the water at the point of entry--the wall--and and pipe it to a point of disposal, usually a sump pump to pump it out of the basement. The picture below might help explain. If you Google "interior basement drainage system" you'll get a ton of hits for different companies with explanations of how their product is installed.

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#46 ·
He has mud deep inside the house which might be deeper than the footing so draining it that low could weaken the footing so stopping the water from the outside and just giving the inside time to dry would be the best bet. You don't want to wash the dirt out from under the footing.
It may even be to late for the footing but the on sight people will have to figure that out.
 
#44 ·
@jim_bee has some good info. Just going to echo that preventing the water infiltration to begin with is best. The sump is need since there is no practical way to prevent what the sump is doing. For that wall that is bowing, the interior drainage does not help that and in my opinion is a work around.

It might be a long-standing work around but likely not what I would consider a fix. I look at it is treating the symptoms rather than fixing the root problem...
 
#50 ·
I know enough to know that putting it off will just result in bigger problems down the road. I’m thinking long term. I guess that comes with getting older.
661894

The cinder block on the side opposite the bowing wall is like this. It’s also like that on the other walls but not as bad. I have taken a thin metal rod and pushed it down in the dirt right up against the wall. It goes down a few inches and hits something. I did this in a few places and had the same thing happen.
 
#51 ·
I know enough to know that putting it off will just result in bigger problems down the road. I’m thinking long term. I guess that comes with getting older.

The cinder block on the side opposite the bowing wall is like this. It’s also like that on the other walls but not as bad. I have taken a thin metal rod and pushed it down in the dirt right up against the wall. It goes down a few inches and hits something. I did this in a few places and had the same thing happen.
Frost depth is the deepest you would ever get frost in your area.
The bottom of the footing has to be below frost depths.
So your warped wall is about 7 ft deep and you would expect to find the footing close to inside dirt level.
But on the other side of the house with a lower ground level you would expect the footing to be deeper.
 
#73 ·
Contractor wants to put in 9 I-beams to stabilize the wall. Plus an inside drain system. Installing an outside drain on the bottom of the wall wouldn’t work because of the level of the creek behind the house.

Wall anchors that attach to a plate out in the yard won’t work unless you know the carrying capacity of the soil. Helical tie backs won’t work because if, when they are being drilled in, you hit a rock they won’t work properly.

I never thought about I-beams and I never thought about the level of the creek affecting a footer drain. If it floods, water will come back up in the drain.
 
#74 ·
Wait for the next guy, he is selling his product more than solving your problems.
The water coming in is creating the mud but the pressure out side is what moved the wall. The I beam tie into the house and the floor.
I don't know how he would tie it in with out a floor but what if the next time the pressure built up. could it move the house with the wall?
 
#85 ·
If I recall correctly, you've got at least one more contractor who is going to look at it. Don't make a final decision until you get at least one more proposal. If you can get three, comparing the methods and cost will give you better information about what is the most reasonable solution at the most reasonable price. You might decide to pay a little more for a solution that makes more sense to you.

Fix'n it is right that you can connect an outside drain to a sump pump. One question that occurs to me now is "what is the elevation difference between the "typical" flood stage of the creek after a heavy rain and your foundation. That will affect the water control part of your solution.
 
#86 ·
If I recall correctly, you've got at least one more contractor who is going to look at it. Don't make a final decision until you get at least one more proposal. If you can get three, comparing the methods and cost will give you better information about what is the most reasonable solution at the most reasonable price. You might decide to pay a little more for a solution that makes more sense to you.

Fix'n it is right that you can connect an outside drain to a sump pump. One question that occurs to me now is "what is the elevation difference between the "typical" flood stage of the creek after a heavy rain and your foundation. That will affect the water control part of your solution.
He wanted to drill weep holes in the block at the bottom.
 
#87 · (Edited)
I am not onsite and would always defer to someone who is. That said, for the type of work you are looking at, I would get at least 3-5 quotes. In my area, that would mean contacting on the order of 4x that many due to no response/time/interest.

For my thinking, it's not just the elevation difference of the flood level of the creek, but also the size of the drainage basin up-slope from the house on the bowed wall side. It appears soil type around the foundation is a problem as well. Even slightly expansive soil exposed to a moderate amount of water would bow a wall like that; you add in the high volume of water from the drainage slope, I do not see a fix that does not involve outside drainage similar to what @Nealtw has shared.

Ask lots of questions and educate yourself as you have been doing. Sometimes these contractors focus on fixing what they see in the basement rather taking in the entirety of the problem. In their defense, a lot of HO's just want cheap & fast so they focus on addressing symptoms rather than addressing root cause. If you ask good questions, you can maybe get them thinking about it a bit more...
 
#88 · (Edited)
@Anduril - I have a friend who had to have a new foundation put in a few years ago on an old farm house. Something that saved him a bunch of money was hiring the excavation work himself instead of having the foundation company sub it out/rent equipment. He had a neighbor with a backhoe that did it and saved him a ton.

Not sure if that would be option but might be something to ask about. For my family that are in rural areas, seems like there's always someone that has that equipment and will do it inexpensively...