# Forum Home Renovation Retaining Walls  Is plastic behind concrete sleeper retaining wall needed?

## solcom

Hi,
I am building a 1.0m high concrete sleeper retaining wall under my house and will be installing 65mm drainage pipe with filter sock at base of wall, covered with 300-400mm of 20mm Scoria. 
Just wondering if there is a need for builder plastic behind the wall? 
I will be extending the existing house floor and plaster wall to approx 350mm from the retaining wall.    
Your advice would be appreciated

----------


## pharmaboy2

Sounds like you have potential water there? 
answer to that is good drainage and geo tech fabric - it breathes but also stops dust getting into the drainage material

----------


## Snipper

I always run the thicker black plastic behind retaining walls.   Preserves the timber sleepers a bit more and stops dirt and weeds coming through the inevitable gaps.

----------


## Marc

+1 for geotex on the ground and up the soil you want to retain, then aggregate between fabric and wall, with drain at the bottom. No plastic for me.
The only time I used plastic on a retaining wall was when I had a wall that was getting wet from one meter of soil accumulated behind it on the neighbour's side. 
Hired an excavator, dug out a trench next to the wall all the way down the footings. Washed the wall and paint it with black roof paint, then pinned black plastic against it. On the soil side I put geotex with extra fabric to fold over the aggregate that filled the trench. At the bottom of the trench an AG pipe draining away from the wall down a slope. The wall dried out in a month or so and been dry ever since. 
But not a typical retaining wall situation. Retaining wall must drain from everywhere possible. Water can push a wall down so better safe than sorry.
PS
Make it 100 mm ag pipe and make sure the geotex shields the pipe too. The sock is sort of academic since it clogs up easily and then you have no drain

----------


## phild01

Plumbing supplies may have something similar to this:   VersiDrain 8 Geo is a dimpled plastic sheet that provides effective drainage and waterproof membrane protection on foundation walls and other underground structures.

----------

