100mm perforated pipe... recommendations

[JackOrion]

We've got a 3m high gabion wall going up behind the house. Gabion designer has specified:

 

"Wavin or similar perforated coil drain 100 Ø mm"

 

Struggling to find Wavin products anywhere (rebranded as Osma?)

Any brand recommendations from here? Unconvinced by stock at the local builders merchants. Naylor / Brett Martin have come up online... any thoughts appreciated.

 

[SimonD]

https://www.travisperkins.co.uk/land-drain-and-ducting/wavincoil-land-drain-pipe-coil-100mm-x-25m/p/711879 or 

[JohnMo]

Aren't gabions free draining - isn't that one the points of a gabion? I would ask your designer what the perforated pipe brings to the party?

[Alan Ambrose]

Maybe this is to drain the water away which runs to the bottom of the gabion. Any manufacturer's perf drainage pipe will do. 

[scottishjohn]

that will be because over time the back of the gabion could get cloggedwith silt -so he wants a drain at bottom to carry it away 

Isusepect any make of perforated land drai nwill do - make sure you surround it with pea gravel so it odes not clog 

a 3m retaing wall could hold a lot of water andturn into slurry which would take your wall away --that why he wants a seperate drain to stop this happening 

 could also be the type of ground you are in 

do you have a concrete found for the gabion ?

when i did mine ihad about 12" of rock rubble behind the gabion for the first m from the base to stop this happening 

Ialos have mine filledwith granite wste from the quarry  -my ground is very free draining

[JackOrion]

Thanks all.

 

Yes, will be using pea gravel and T1000:

 

Wavin or similar Perforated coil drain 100 Ø mm surrounded by geotextile Terram 1000 or similar and 10mm single sized pea gravel, connected to outlets at 15.0m max centres.

 

Baskets will be on a 300mm SHW Type 1 sub-base. And below that sub-base we need to put in drilled piles that are tied into the foundations (also on piles) via ground beams. Quite a bit for a single storey 2-bed timber frame.

 

On top of that we have tonnes of natural stone on site, but our gabion designer is insistent we use Class 6G gabion stone only, so having to bring that in.

[Roger440]

22 hours ago, JackOrion said:

Thanks all.

 

Yes, will be using pea gravel and T1000:

 

Wavin or similar Perforated coil drain 100 Ø mm surrounded by geotextile Terram 1000 or similar and 10mm single sized pea gravel, connected to outlets at 15.0m max centres.

 

Baskets will be on a 300mm SHW Type 1 sub-base. And below that sub-base we need to put in drilled piles that are tied into the foundations (also on piles) via ground beams. Quite a bit for a single storey 2-bed timber frame.

 

On top of that we have tonnes of natural stone on site, but our gabion designer is insistent we use Class 6G gabion stone only, so having to bring that in.

 

You sure about the pea gravel? 

 

That gets blocked up pretty quickly. I always use 40mm stone round my drains.Which is what im led to believe is the right way.

 

In my experience the perforated 100mm drainage products are all much of a muchness. 

Edited yesterday at 20:38 by Roger440

[JackOrion]

1 hour ago, Roger440 said:

 

You sure about the pea gravel? 

 

That gets blocked up pretty quickly. I always use 40mm stone round my drains.Which is what im led to believe is the right way.

 

In my experience the perforated 100mm drainage products are all much of a muchness. 

 

The pea gravel spec came from the gabion engineer, in this case it's within backfill that is specified as 6N. Attachment here.

[Alan Ambrose]

FYI you can get geotextile socks which go over the perf pipe rather than sheet Terram.

[Roger440]

4 hours ago, Alan Ambrose said:

FYI you can get geotextile socks which go over the perf pipe rather than sheet Terram.

 

You can. Not much fun trying to fit them though.

 

Id also say, not ideal as its in the wrong place. You dont want the backfill to get clogged with fines, which the socks do nothing to prevent.

[Roger440]

13 hours ago, JackOrion said:

 

The pea gravel spec came from the gabion engineer, in this case it's within backfill that is specified as 6N. Attachment here.

 

Im no civils engineer, but 6n backfill has fines it it, which will migrate to the bottom, ie the pea shingle and eventually block it up. 

 

Its not what i would do.

 

Mind you, a structure like this behind my house would scare me. Though not as much as the ones ive seen not far from here that use the interlocking wood system. In his case over 4m high with the houses at the top. The timber will be rotted away inside 10 years and the whole lot will fall down.

[JackOrion]

8 hours ago, Roger440 said:

 

Im no civils engineer, but 6n backfill has fines it it, which will migrate to the bottom, ie the pea shingle and eventually block it up. 

 

Its not what i would do.

 

 

The aggregates supplier said similar re: 6N and fines. Will investigate further.