Garden Drainage Issue

[djn2020]

Hello,

I need some advice about the attached.

We have a buidling in the garden that my ASD son uses when relaxing. However, the previous occupants of the house seem to have neglected the drainage.

I have dug down into the gravel that is alongside the perimter of the building and can see that I'll need to do more; namely put in some drainage below the ground and make sure there is an adequate fall to move the water off the property and into a nearby stream.

I'm thinking about a french drain constructed of:

1, PVC perforated pipe
2. Round gravel of adequate size
3. A non-woven, perforated membrane.

My question is related to the soil and membrane - based on my apparent soil type should I be concerned about clogging? Will clogging lead to the drain failing with me having to dig it all up again?

http://www.landis.org.uk/soilscapes/# tells me that the soil in our area is apparently soilscape 6 - loamy.

http://www.landis.org.uk/soilscapes/soilguide.cfm

That said, the soil seems like clay when digging. And as we live in an area where there was once a mine, I think the orange soil is a clear sign of iron pollution.

I've been researching french drains on youtube but there is disagreement about plastic perforated pipe vs pvc, and also on the use of membranes. I have even read some people debating gravel (angular vs round).


Has anyone faced a similar issue with standing water? How did you tackle the issue?

Thanks in advance.

Edit: please ignore the drain pipe. It is only there temporarily. I'll also put in a proper downpipe and dedicated pipe to take that water away - it won't be left to fall onto the ground directly to add to the surface water.

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[djn2020]

Hello. Thanks for the reply - there is someone out there!

As far as my understanding goes, this would work well for water that comes down. However, the issue is caused by water that comes up. That's why I'm thinking about the french drain.

Also - just thought of another question or two. How deep/wide should any trench be? And how far away from the foundations should it be positioned?

 

[JohnD]

Looks like Somerset to me

From the soil, stone and garden

I think the red earth is regional, not pollution

I was thinking of a sump or pond near the building, perhaps with a French drain, around or preferably upstream of the building, then a channel or pipe to the stream

A French drain can be filled with large cobbles or, in your case, clean broken stone, with textile to prevent it clogging with soil. Big stones drain better than gravel. You can put a gravel path on top.

 

[djn2020]

Looks like Somerset to me

From the soil, stone and garden

I think the red earth is regional, not pollution

Hi JD,

Further west than that.

Thanks for confirmin my approach - but what do you think of the details (trench depth/width/clogging etc.)?

 

[JohnD]

I think it's usual to dig a french drain about a spade width, because you use a spade.

it can go close to the house as long as it does not go below foundations. My neighbour has one right up against the house wall to reduce damp in his cellar.

the depth just needs to be low enough that water in the bottom will not be high enough to cause damp.

the fabric will prevent earth and mud washing in to clog it

when you dig a sump or trench, the water level around it drops, but in a slope. It drops more close to the trench but less with distance. I have seen diagrams of this but don't know how it is calculated. depends on the free-draining structure of the ground I suppose.