Land drain/French drain correct way to install?

[ruggers]

I have a site that needs cleared to build on which will require some underground 100mm perforated drainage pipe installed as it sits lower than a neighbouring plot & both have historically been wet woodland. 

The top soil and sub soil seem to vary between 300-450mm (12 to 18") and then its the clay. 

Questions:

 

1. Do I install the drainage pipe onto the top of the clay as this is the lowest point?

 

2. People have different methods of installing the pipe, which is best?

(A) Dig the pipe trench, add a sock over the drainage pipe then surrounding it in stone and then cover with soil.

(B) Digging a trench for the pipe, lining it with a geotextile membrane, lying the pipe into it surrounding with stone, and then wrapping the pipe & stone with the rest of the membrane.

(A) Seems easiest & some say it works, others say, eventually that the soil works between the stones & clogs the sock sleeve & that (B) is the harder but best option to last a life time.

 

I can't understand how the sock/membrane sheet could clog one way but not the other or is this personal preference?

[Conor]

I went with B for our basement perimeter drain. Reason being that it will prevent your clean gravel from clogging up. The gravel does the work 90% of the time anyway, with just heavy rain needing the pipe to kick in, unless you've a high water table. It's easy enough. Just make sure your membrane is wider than it needs to be.

 

 

[ruggers]

Thanks Conor, the last thing i want to do in 10 years is dig it back up so thought it was worth seeing what others do. I have a mate who worked in groundwork & says that (A) is fine but I think (B) will be my preference.

[ProDave]

I did method B

 

But the No 1 question when trying to drain wet land that is lower than the adjoining plot, is just where are you going to drain the water to?  I hope you have some area that is either lower, or drains well, to drain all your water to?

[Temp]

Great site for all things paving and drainage. This is their page on French Drains. Perhaps bookmark their index

 

https://www.pavingexpert.com/drain03#french

 

Index

https://www.pavingexpert.com/pavindex

 

Option B would be the one on the left. The middle option is possibly better if it was all clay and you get standing water. Right hand one is for dispersing output of treatment plant.  

 

[ruggers]

1 hour ago, ProDave said:

I did method B

 

But the No 1 question when trying to drain wet land that is lower than the adjoining plot, is just where are you going to drain the water to?  I hope you have some area that is either lower, or drains well, to drain all your water to?

All of the water drains to a low point ditch but I just want to run a pipe across the high point boundary line so the neighbours water don't run across my land. I can terminate the end of the run into my surface water drain pipe. It's not flowing water, its just wet land in places.

[ruggers]

thanks @Temp I'll have a look and save that, I've seen the site before its really good. Option B seems the way to go really.

[saveasteading]

Option B without a doubt. As well as the point re silting up, the wet gravel is very attractive to tree and other roots, which would soon fill all the gaps. 

It is a pain to do and needs to be quite organised, but worth it.

[Ferdinand]

In the past I have done B using normal plastic waste water drainage (110mm?) pipe with umpteen holes drilled in, and weed membrance as the liner, folded over the top, with a bit more gravel and pavers over to make a path.

 

I now wonder about the Wickes heavy duty membrane and lifting the pipe slightly off the bottom of the drain via a layer of the gravel.

[ruggers]

Thanks. From what I've seen, some have a small later of stone under the pipe, others have the pipe right at the bottom of the trench, but all seem to have the non woven membrane wrapping the pipe and the stone for longevity.