Another drainage issue french vs aco

[tren]

I am looking for advise on damp/water ingress issue with my barn conversion.

Because of the gradient of the concrete courtyard water flows towards the barn and accumulate above floor level in front of the door (and to the back of the building). Water/damp makes it's way in the building eventually.

I have started digging up the concrete in front of the door and to my surprised I uncovered an old concrete gulley along the wall which is lower than floor level. However that does not solve my problem:

1. one the gradient goes to the left of the door and has no where to go so there will be pooling anyway (I could potentially install/reroute a drainage pipe there connected to my soak pit)
2. they broke part of it to run a 4inch pipe for the gutter (that is not at the lowest point of the gulley) and a conduit for an electricity cable (not needed anymore).
3. I think the gulley only runs to the front of the building not to the back where I also have damp issues.

I have scrolled the forum and the internet and am still wondering what is my best solution to solve this issue in the most cost effective way possible but also how we could tidy up the area at the front at the same time.

What I have in mind so far:

Option1 - french drainage system

• dig all the concrete up in front and back of the barn (approx 2m wide)
• dig a french drain along the wall and install perforated pipe and membrane connecting it to existing soak pit.
• Top the entire area up with gravel keeping it below floor level to have a nice and tidy front area

I have read on here that this might not be the best solution as it might not help the wall to breath and dry?

Option 2 - Aco drain all around the building

My concerns with that solution is:

• My levels are all over the place so I would need to essentially install it much lower than the existing concrete level in some places.
• The granite stone are not flat so my Aco drain won't be able to sit nicely against the wall. Is that a problem? What shall I fill the gap with if not?
• It won't leave me with a tidy and clean outdoor area, we don;t have the budget to pave or anything like that at the moment

What would you do? Any other suggestions?

 

[Cubist]

Personally I would favour a French Drain sited near all the exposed perimeter walls as per that you describe. I'm not sure where on this forum you may have found a suggestion that such does not help the walls to breathe and dry but from personal experience here I can tell you that's a false conclusion. However, to get best result you need to follow the 'lie of the land' to ensure that the drain works effectively to direct water to the lowest available level and that the final exit is kept as clear as possible.

ACO drains can be very effective but rely on the same principles but their modular (circa 1 metre lengths) can induce installation difficulties on top of their greater cost.

 

[Janela]

My feeling is also a french drain as this removes water from the soil an ACO drain removes the surface water when it rains but not the stuff already 'running' through the soil.
It is usual (at least in these parts) to site the french drain about a meter out from the house on the grounds (pun not intended) that if you put it right against the wall it can cause movement if it dries too much.
After that you could also try a Zebcolm trench (see this site) if required which airs the wall, as opposed to removing the water from the surrounding soil.

Another consideration is your soil type.
If you are on heavy clay your soak pit will just fill and the water will sit there, in which case you'll need to take it away further.

 

[tren]

Thank you both, that is my gut feeling too with regards to French drain vs Aco drain. We are in Cornwall right by the coast so no clay here but lots of granite!

I was going to remove the concrete gulley which is right against the stone wall and dig my trench between 1 to 2ft away from the wall. Would that be ok?

What depth would you dig the trench? 1ft at highest point and 2ft at lowest ok?

I have a soak pit a few meters away from the building so I will connected my perforated pipe to that. There is a 4inch gutter pipe already that is intended for the gutter so I would think/hope it should be fine to connect the french drain to that in terms of capacity.

 

[Cubist]

The foundation/footings of those stone walls will be massive, 1 foot distance from them may be optimistic but that's what I would try for. It may also be an idea to use the outer edge of that stone gutter as the boundary line. I foot depth at the higher levels of the ground around the building would be reasonable too.