Protecting shed slab with drainage pipe


  #1  
Old 03-24-09, 07:23 PM
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Protecting shed slab with drainage pipe

I'm pouring a 12x8 floating shed slab and think I need to install drainage pipe around perimeter to protect it from heaving. My questions are do I need to install the drainage pipe and how to install it.

Slab site is on my side yard at base of a hill, and the long side is about 30 degrees from perpendicular to the incline. Incline extends about 25' up from shed wall until it ends at neighbor's house. Total rise is around 3' over the whole 25' span. It's the water coming down this hill that worries me. Soil is very sandy and well drained. I lived in Maryland (plant zone 6a). Frost line is 3' down.

Is the drainage pipe a good idea or overkill?

Assuming I need the pipe:
-how deep should pipe be?
-how much gravel do I need under, beside, and on top of pipe?
-any easy way to estimate gravel amount, such as X gravel per foot of pipe?

I assume install procedure is to dig a shovel wide trench, set downhill incline, lay filter fabric, add gravel, lay pipe, more gravel, wrap fabric closed, and back fill with soil. If necessary, I could also extend pipe additional feet off downhill side of shed.

Thanks in advance for your advice.

Dave
 
  #2  
Old 03-25-09, 04:41 PM
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My thoughts,

On a slab like that you still want to put a 6 deep key way around the slab. That will help with any water getting under the slab and it will prevent the slab from moving during the freeze/thaw months. You could still install a drain pipe but I think I would just go with a grass swale along that side of the shed. The one bad thing about a underground drain is. In the spring when you get a warm day and the snow is melting, the ground is still froze and so is your pipe, where a swale will all ways be there.
 
 

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