Drainage Tile For a Slab Foundation?

September 16th, 2009 by Doug
DIY House Basement and Forms

Basement and Forms

Now that the block is done I could start getting the concrete slab ready to pour.  I still needed to rough in the plumbing and fill the slab with gravel which will take some time, but I began to wonder about drainage tile.   When building the basement for our home six years ago, we went out of our way to ensure water stays out. But what about on a slab foundation?  After some research on the subject, I came to the conclusion it would be cheap insurance considering water and wood don’t mix well and I am building a log cabin.

Drain tile has a pretty straight forward goal of trying to keep ground water away from the building.  It is nothing more than a pipe (usually 4″ diameter) that has holes or slots cut into it that gets buried around and below the grade of the slab.  The pipe is then covered with “clean” (no dust) gravel and is also covered with some type of landscape material to keep mud from clogging the pipe.   The ends of the pipe are trenched out and away from the foundation, usually towards lower lying areas.

Tile Installation

17 drainage tile by hand

Drainage tile by hand

I chose to only put tile on three sides of the foundation as it sits on a slight hill and the back of the cabin should naturally shed water.    Since my footings were still exposed from doing the block, I placed the pipe on top of the footings.  This was well below the slab floor and should do a good job of keeping the water at bay.  I still had to pay attention to grade as standing water is never good.  Once the pipe was down I covered the pipe with the landscape material to keep out fine particles that could clog the slots.  After this was done, “clean” gravel was applied almost up to grade as I plan to back fill and build up around the foundation some.

18 drain tile done

Drain tile done

Up to this point most of the work involved laying out pipe and running the tractor (gravel), but now I needed to trench in the tile exit points.   Word of advice; don’t do what I did, please rent a trencher.  I spent almost two days (ok evenings after work) digging the last 10 feet of each tile!  While it was a great workout, digging a four foot deep trench by hand is not fun!

Project Materials and Cost

$45 – Slotted corrugated pipe (100′)   – Lowes
$10 – Unslotted Corrugated Pipe (20′) – Lowes
$35 – Landscape Material (100′) – Lowes
$175 – Truck Load of “CA6 Clean” gravel (3/4″) (14 tons) – Quarry
$265 – Total Cost

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