drain tile well below footing... is this okay?

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  #1  
Old 09-21-14, 01:39 PM
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drain tile well below footing... is this okay?

some things should be left to professionals... but it's fun to try myself and learn something new...

with regards to my drain tile... my excavator went 10 to 12 inches below the top of my footing... the footing for the existing part of my house is only 5 inches deep and so there is clay/soil exposed below it. The new footing for the foundation for the addition will be dropped 4 inches and will be 8 inches deep.

Typically drain tile should be sitting on a few inches of rock just above solid ground so that the water doesn't build up too much before entering the drain tile.

Is it better for me to drop the drain tile so it's only a few inches above the solid ground with lots of drain rock on top? In this case the top of the drain tile might just be at the bottom of the existing footing... is this okay?

Until now I had the black flexible tubing and it was totally clogged and I had no basement issues so I figure whatever I do will be better than before I am just worried the clay under the existing foundation may become unstable.

Any comments would be appreciated. I am new to this forum. Will upload some pics if that helps.

NOTE: I will also be adding a closed rain water leader system to the storm connection as well. From what I have heard in our parts 75% of the water that reaches the foundation is rain water from water leaders.

I have plenty more questions but this will get things started.

Cheers
Daniel
 
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Old 09-21-14, 05:19 PM
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A few inches below the bottom of the foundation footings is normally not a problem.

Except...

You may not dig below the bottoms of the footings close to the footings otherwise the soil and then the footings and then the foundation could collapse. A good rule to follow is to not carve below an imaginary slope (plane) going away from the footing bottom at a 1:3 gentle slope. That is, if you need the bottom of the trench 4 inches below the foundation footing bottom then the trench has to be a foot in (or a foot out on the exteior).

Unless new surface water percolates down too rapidly, the drain tile 6 inches below the footing will capture water just as effectively as a drain tile next to the footing. (Too far down and the drain tile will perform less and less well.)
 
  #3  
Old 09-21-14, 08:47 PM
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thanks for your response. I don't think I'm in as bad as I had thought. I have 4' stem walls and so hopefully the backfill will add support as well - I will tamp it down good especially at the bottom. Can't wait to get my foundation poured and the drainage started...
 
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