Below Grade Mono slab drainage problems

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Old 04-02-10, 12:55 PM
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Below Grade Mono slab drainage problems

I hope someone can help me here or give me some advice....

Here's my story: We bought this house about 2 years ago in Southern MD (low sea level, high clay and water table). When we bought it the basement did not leak. The new drywall should have been a sign but thats another story. Anyway, it wasn't until the first big rainstorm that we had, did I discover a 1/4 inch of water in the corner of the house. The particular corner was the corner of the house that was in the direct path of the direction of "flow" or downward slope of the land. After a few quotes from various contractors (one of them being Atlantic waterproofing, again another story) we decided to try to tackle the problem ourselves. I did a bunch of research before we started work. So here is a list of things that we did to attempt to rectify the problem:

1. dug up the old perimeter (footer) drainage system. It was old and crusty.
2. replaced it with 6" drainage PVC (white, stiff, holes drilled on bottom half of circumference) along with 4" of pea gravel on the bottom. Pipe was placed at footer level. followed by 8-10" of pea gravel on top using landscaping cloth on top and bottom of pea gravel and a sock over the pipe. Pipe drains to an existing drainage pipe away from house and with slope of land.
3. backfilled with same dirt that was dug out
4. diverted gutter drainage away from house
5. sloped back fill at least 1' for every 6'
6. installed a sump pump in central location in house

A few specs about the house:

-30'X50' raised rancher
- back left corner basement is 6' below grade opposing corner is at grade (if that makes sense)
- basement/house foundation is monolithic pour with CMU block walls
- Leakage occurs at bottom of basement walls and usually only with heavy rains


AFter major foundation drainage replacement it seemed to have fixed the problem. However a few weeks/months later same problem. considerable less water, but any water is unacceptable. Obviously I can't dig a trench drain on the interior because of the mono slab. I've seen a few companies that want to come out and give estimates of their fabulous products for $2500-5000 a pop. Im looking for something I can do myself. Can anyone help? I can send pics or images if anyone would like...please advise if you can!!
 
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Old 04-02-10, 05:45 PM
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Is water entering on all sides of the house? If not, how many sides are affected?
 
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Old 04-02-10, 05:57 PM
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If you used the original "dirt" to backfill above the drain tile area, you could have prevented the drain tile form stopping flow to the drain tile. Well draining material should have been used, especially if the slope is away from the foundation.

What coating or waterproofing was applied to the exterior of the portions of the walls below grade?

Dick
 
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Old 04-02-10, 06:06 PM
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[IMG][/IMG]


Maybe this pic will help out...
 
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Old 04-02-10, 06:09 PM
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How much water comes out of those footer drains when water comes into the basement?
 
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Old 04-02-10, 06:10 PM
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I used a rubberized asphalt material (not sure of the brand) but was specifically for treating walls for exactly this type of use.

So you dont think I should have backfilled with regular dirt? What would it matter if water couldn't get to the drain? where the water is comming in on the inside is under gravel and drain pipe on the outside.
 
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Old 04-02-10, 06:13 PM
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Originally Posted by drooplug View Post
How much water comes out of those footer drains when water comes into the basement?
Honestly Im not entirely sure how much. I know water does come out, but I haven't watched it closely enough to see how much.

Are you thinking that it may be clogged or slow???
 
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Old 04-02-10, 06:26 PM
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I've used that material many times against the foundations. As long as you went a few inches below the footing, it should be ok. A few inches of gravel should have been thrown to the bottom before before you back filled.
 
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Old 04-02-10, 06:43 PM
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Originally Posted by Pulpo View Post
I've used that material many times against the foundations. As long as you went a few inches below the footing, it should be ok. A few inches of gravel should have been thrown to the bottom before before you back filled.

it was...about 14-18 inches...
 
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Old 04-03-10, 07:26 AM
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Things can go wrong, so you might have to open the hole again but it sounds like you did the right job, to me.
 
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