To ACO drain or not?

[happytimes]

Evening all — patio gravel too close to DPC, looking for thoughts on two solutions

Looking for some advice on rectifying a gravel/patio setup that was laid too high relative to the house — the gravel is breaching the DPC. No internal issues yet but keen to get ahead of it.

The diagram hopefully gives enough context, but in summary: the wall has brick piers between the windows which make it impossible to run a continuous ACO drain solution in and out. I have dug the trench down to the bottom of the first concrete block already. I'm intending to cut back and relay the slabs closest to the house to create space for one of two approaches:

Option A — Create an airy trench filled with cobblestone around and between the piers, sitting just below the DPC. A physical barrier between the cobble and the surrounding gravel/patio keeps the cobble contained and a few centimetres lower than the DPC without the gravel migrating across.

Option B — Run ACO where the geometry allows, using it as the physical barrier between stone types. Cobblestone fills the trench between the piers under the windows where ACO isn't viable. The existing soakaway point can be reconnected.

Both options use cobble specifically to keep the trench airy rather than packing a damp material against the wall.

Which would you go with, and is there anything in either approach you'd change?

Thanks in advance.

 

[^woody^]

Bear in mind that if you have a cavity wall, then it won't matter if any gravel is above the DPC.

I can't see why you would need surface drains if you have that gravel between slabs which water is going to drain through not run over.

Cobbles won't make any difference either. It will just make an uneven surface with massive gaps between the stones, and no practical advantage.

 

[happytimes]

Good point on cavity. I guess I was mindful of the amount of window reveals potentially breaching the cavity. The space between the majority of those pavers is solid with a few gaps that drained to the earth. The first 5 mortars of the piers are always noticeable wetter looking even in the summer - was concerned about long term impact. The gravel in the window areas was sitting on some very compacted ground, very close to the DCP so I don't think its had adequate draining. I'm still keen to increase the separation between the columns and pavers (less than 5mm atm). Taking your advice - as I've now removed the compacted ground and pea gravel - I could just fill it in again with a larger one 40mm - lots of drainage lots of air then. I'm replacing all the existing gravel anyway as the little stuff goes EVERYWHERE. What do you reckon? Thank you much appreciated

 

[^woody^]

Is the paving actually sloping down towards the house, or is the damp on the walls from rain splashing up the wall?

 

[happytimes]

Not sloping towards - overall slopping parallel to the house. (To the left)
Have attached a photo to show an example of what the brick looks like now the gavel/silt mix has been removed. That tide line is above the DPC. Cheers again