Considerations of gently sloping site

[Owain1602]

I'm not exactly sure what my question is.

 

The barn which we'll be converting is positioned in a field which has approximately 2m elevation change across a 40m length. The field slopes down towards the barn, but continues to slope away beyond the barn, so it's not like a bowl. We'll need to dig out the highest side and create a retaining wall (~1m high).

This got me wondering what the concerns are when digging in to a bank, particularly with regards to drainage of the fields above the barn/retaining wall. The site is one of the highest in the county, everything slopes away from us, and the ground is said to be very sandy and remains dry all year round.

 

I presume the concern is that heavy rain could saturate the ground, causing further rain to flow downhill along the surface of the ground (a river). This must be a particular issue for poorly draining soil (such at clay), where the ground becomes waterlogged due to water not being able to freely drain downwards through the soil. But with very sandy ground, could this still be a concern?

As a slight aside, we have a long 1m high retaining wall (rail sleepers) in our current garden with the entire garden above the retaining wall sloping down (1:10 gradient). We have never seen any water coming through the sleepers. 

[Russell griffiths]

There’s not really a question there, just your observations, and you sort of answered them. 
Retaining walls, use something flexible, gabion baskets, natural stone, timber, don’t use something solid and inflexible, blocks rendered, concrete rendered. 
this block rendered white trend is a recipe for old tired cracked retaining walls, but it looks trendy in the world of porcelain slabs and fake grass. 

[JohnMo]

We sculpted out a hill quite a bit more extreme than yours. So anything is possible.

 

Formed out a platform for the house to sit on, moving many thousands of tonnes, but took nothing away from site 

 

Retaining walls were done with gabions near the house, and wooden strainers elsewhere (8" wooden posts)

 

A before and after

 

[saveasteading]

A slope is an asset. Your drainage can follow it and not get deep. 

In sandy soil if you use perforated pipe,  only severe rain will reach the end. All your manhole and such, and digester of there is one, are also  shallow.

 

You might not need it , but can add a drain before the retaining wall, taking water ro the side.

[joe90]

+1. I consider a slight slope an asset for the above reasons plus you say you are the highest point so no or very little drainage from above. AND sandy soil, what’s not to like 🤷‍♂️

[ToughButterCup]

There are many benefits to a sloping site. Not least to assist in our SUDs program.

The slope towards that sycamore tree in the background hides a pond. That takes every drop of rainwater from our roof. The slope hides all sorts of small horrors (to be dealt with in due course) and provides privacy and shelter for many.

 

(PS @JohnMo, that's a wonderful build and site)

Edited November 10 by ToughButterCup

[Owain1602]

Thanks for the replies, I thought it was all good news but wasn't sure if there was something I was missing. 

 

@JohnMo That is a great site you have. Can't quite make it out from the pictures, but do you still have a large slope leading down towards the house from the back? If so, did you put any drainage provision in for water coming down the bank?

 

@saveasteading I think I will put some form of drainage pipe behind the retaining wall just to encourage the water around the house

 

Maybe for another thread, but another question that comes to mind with a slope is, can you have too much slope on the foul drains leading from the house to the treatment plant? I'm aware with some drainage that too much slope means the water/liquid travels through the pipe too quickly, leaving solid material stuck.

[saveasteading]

1 hour ago, Owain1602 said:

you have too much slope on the foul drains 

Yes. It is all covered in the building regs where graphs show grades.

Let me know if you need help to find it.