Aco/French Drain?

[junglejim01]

Following on from my post bout tanking, i'm now low looking at solving the problem from outside.
The problem: penetrating damp from raised groundlevel, 1ft above inside
Possible solution: Double drain: land drain below internal floor level with Aco drain on surface. And membrane against the wall.

Any thoughts, experience etc on this?
Thanks

 

[junglejim01]

Another builder has suggested the following:
"i would suggest we dig out along the wall and create a barrier between the wall and the aggregates using a medium dense breeze block then bed the channel on top."

I hadn't considered this as i was thinking of getting the water away from the wall. Any thoughts?[/i]

 

[^woody^]

You could get 50 builders around and get 50 "suggestions"

If you have penetrating damp, then you need to determine the main cause and deal with that.

An ACCO drain will be useless if you have a high water table or otherwise very porous walls - which sandstone is.

External barriers are often ineffective, as it is very difficult to create an actual barrier

So if the walls are the issue, then deal with those and then there is no need to worry about external ground levels or water

 

[junglejim01]

Thanks for the advice. My thought was that by installing a land drain we could take water away from the walls in a similar way that a French Drain would work. I'd welcome your suggestions on how else i could deal with the walls.

 

[^woody^]

But the ground will still be wet, and the potential for penetrating damp would remain

It is a solution, but it may not be the solution.

You are aware of the possible remedial work - internal tanking, external barriers lowing ground, removing excess water etc, I can't add anything to that.

IMO, this is something that needs looking at by someone experienced who can assess everything and come up with a suitable solution, which does not involve trial and error and suggestions

 

[junglejim01]

Cheers again. Yeah in the ideal world i would drop the ground level. I might be able to gain a couple of inches but nothing more unfortunately. I'm definately not an expert and am getting a range of opinions. My thinking originally was a French Drain below internal ground level and connected to existing drainage pipes. Surely this would ensure that water is taken away from from the wall? Am i missing something or overcomplicating it?
Cheers

 

[junglejim01]

apologies...didn't realise i'd posted twice

 

[^woody^]

Ground is constantly damp. Your other thread states that you have sandstone walls underground, and this is a very permeable material (takes water) and is very porous (holds water) ie it is like a sponge, and would not require a great deal of localised water or water under pressure

So no matter what you do it would seem that the wall below ground would will be constantly damp.

This may well require a physical barrier of some sort, and as one externally may not be easy to form, it may mean that an internal barrier is required

That is why you would be better off with some experience person looking at it and taking every factor into account

 

[Norcon]

Dig down then shutter a wall of concrete against the sandstone wall. A few feet? Childs play.
If you hit any founds then benonite these. And benonite up the sides.
If no founds then benonite the wall.
Then apply a good quality membrane. We use Bitusheet XL as shown in the link.
http://www.sdg.ie/waterproofing/tanking-membranes/bitusheet/
Then pipe and backfill with stones , rocks etc and compact well as the benonite will exert some pressure when it expands. Job done.