Retaining wall drainage

[jmhill]

Hi,

I’m building a retaining wall in my garden a need to put a drain at the foot of the wall.

I was going to use a perforated 100mm flexible pipe in a geo textile sleeve bedded in gravel but I can’t find a product that would allow me to T off smaller diameter weep holes at regular intervals, what can I use without spending the earth, or should I just bing the pipe out of the wall at one end and allow water to drain out that way?

Thanks in advance,

Jon

 

[KenGMac]

jmhill, good evening.

There is no hard and fast rule as to whether there should be weep holes in the length of the wall or not?

If the wall is long then weep holes should be a consideration, in case the perforated flexi blocks down stream of a [potential] weep hole.

Generally, the geotextile is taken up the inner face of the retain wall, indeed the area behind the retain wall should be infilled with aggregate, many specifications advocate a single size aggregate, the geotextile is taken up to ground level against the excavated earth, in effect, you have a sort of three sided encapsulation of the aggregate.

If the wall is high then turn over the geotextile again to encapsulate the aggregate. the geotextile acts as a barrier to small particulate that will over time block the perforated drain.

As for installing intermediate weep holes? you should know the level of the pipe invert, simply drill a hole through the wall and insert a plastic pipe, this is undertaken as a retro job, when the wall has been constructed , the pressure of earth above will hold the geotextile in place and form a seal between weep pipe and the aggregate.

As for the perforated pipe? you may wish to consider running the perforated pipe to the surface at the "top" of the run [the upper end] this will allow the perforated pipe to be cleared should a blockage occurs.

Ken.

 

[jmhill]

jmhill, good evening.

There is no hard and fast rule as to whether there should be weep holes in the length of the wall or not?

If the wall is long then weep holes should be a consideration, in case the perforated flexi blocks down stream of a [potential] weep hole.

Generally, the geotextile is taken up the inner face of the retain wall, indeed the area behind the retain wall should be infilled with aggregate, many specifications advocate a single size aggregate, the geotextile is taken up to ground level against the excavated earth, in effect, you have a sort of three sided encapsulation of the aggregate.

If the wall is high then turn over the geotextile again to encapsulate the aggregate. the geotextile acts as a barrier to small particulate that will over time block the perforated drain.

As for installing intermediate weep holes? you should know the level of the pipe invert, simply drill a hole through the wall and insert a plastic pipe, this is undertaken as a retro job, when the wall has been constructed , the pressure of earth above will hold the geotextile in place and form a seal between weep pipe and the aggregate.

As for the perforated pipe? you may wish to consider running the perforated pipe to the surface at the "top" of the run [the upper end] this will allow the perforated pipe to be cleared should a blockage occurs.

Ken.

Thanks Ken

I imagined the perforated pipe would run behind the length of the wall and the smaller diameter pipes would T into it and run at 90 degrees through the wall forming the weep holes, is that not right?

Regards,

Jon

 

[KenGMac]

Jon.

Short answer, YES!

Ken