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Discussion Starter #1
This is not what I usually work with and am looking to sub out an issue that came up removing old flooring in the basement. I have a residential job where the basement has footers 3' below the poured bsmt floor. Looking to have a new interior drain system installed to replace the failed clay tile system that was installed a few inches below the bsmt floor. Where should the drain be? I was under the impression the drain should be at the footer. A few companies have quoted the job but say that it doesn't need to be that deep to relieve static pressure. This house has had water issues to the point where the bsmt floor has fallen 4 inches in a few corners. I have fixed all the downspouts and grading on the exterior now I want to make sure the sub installs the proper solution on the interior.
 

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What do you mean when you say drain?

You don't list your location on your profile. In this area, we use 3 or 4" perforated drainage tile around the interior and exterior of the footing, with the top of the drainage tile flush with the top of the footing.

What is under the slab in question? Sand, clay, pea gravel?

If you have 4" of settling in a corner, I would like to have you remove the slab and start over, at least the worst pieces.
 

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Here is where it stands. The entire interior perimeter has been cut and jack hammered 16" off the wall. All old clay drain tile that was installed just below the slab had failed due to the soil below settlement. I believe the settlement is due to the poor water management on the exterior as well as the placement of the original drain tile just below the poured slab and not 3' down at the footer. The original sump pit 22" has been dry for years. Its been dry because the original drain tile had fallen with the slab 3-4" in some areas. Water was trapped. I dug down in a few areas to find the footer depth at 3' below the basement floor. All cinder block weep holes were originally drilled at floor level. My question is where should the drain tile be located? My feeling is it should be next to the footer not 3' higher just below the floor. Once you dig down to a foot just above the footer there is water in some areas, particularly along the back wall. The front wall is below grade. The back wall is at grade with a patio slider walkout. then back yard continues to slope down.

House is in central MD between Between DC and Baltimore.
Soil is sandy till about foot down to the footer. Then you start run into clay and water in areas. House was originally built with an interior drain system nothing exterior. Cinder block walls.
 

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A little confusing, but maybe a little more info.....

First off, was the clay excavated initially, or was the footing dug/poured only around the perimeter? You've got a walkout, and you're at grade there, so I'm guessing the 3' depth is to satisfy footing depth requirements......?

You say the sump pit is dry, but the water is 'trapped'.......and that you hit both clay and water about 2' down.......so what takes care of water removal? Is it gravity? Or a pump in the sump pit?

I'm guessing that the sinking is primarily due to poor compaction under the slab.......I suppose it's possible that poor water management on the outside could cause the slab to sink on the inside, but I've never heard of that.....:blink:

I would likely defer to the (qualified) guys in your area who do this for a living.....I think neither (at footing or just below slab) is wrong.....but if you plan on using a pump, having it 3' below the slab may have it working far more than it needs to.......
 

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Discussion Starter #5
The original weeping system was located a few inches below the slab. When I dig down I encounter water below the old weeping system but above the footer. The majority of the soil beneath the slab has settled compromising 75% of the slab. The footers and block wall have had minimal issues. I did point up a few areas with minor cracks in the mortar. None of the walls have moved laterally. My concern is really with making sure the footers will be good in the future and try to stop anymore settlement for the four the new slab.
 

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What you describe sounds as if the soil was not compacted when the walls were back filled.
If properly compacted I would not hesitate the install the interior drain system as typical and a few inches below the bottom of the slab.

Drain system placed lower will not drain to the sump crock.

Is this your home?
 

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Discussion Starter #7
Thanks for the feedback. No this is not my home. Took on a job for a relative that has taken me further then I anticipated.
 
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