1810 house - French drain or Aco drainage - No DPC

[tvrulesme]

A recent damp and timber survey discovered raised external ground levels which are one of the things causing damp walls inside the house. Please note this house was built in 1810 and has no DPC. The surveyor suggests the following:
 

Form a trench at the wall/path junction to a depth of 150mm below the physical damp proof course or internal floor level and fitting Aco drainage or similar, discharging into suitable drainage or back filling with pea gravel to allow drainage of rainwater.

Any gravel filled trench should incorporate a suitable membrane against the wall surface and drainage so that water does not pool within the trench, which over time would penetrate to the full thickness of the wall contributing to internal dampness. Guidance on how to install such a membrane and drainage can be obtained from manufactures websites.

A couple of questions:

1. I am leaning towards a French drain because it has more flexibility for getting around potential obstacles, is less permanent if things go wrong (rip it out and replace etc), and does not need to be physically fixed in place introducing more impermeable substances into the area with damp. Is this logic sound or am I missing something?
2. Does anyone have an idea of what sort of membrane he may be suggesting? I can follow up with him but just wanted an opinion on here
3. Given the age of the property and it's construction am I missing a trick where something else would be preferable?

A few pics for reference attached

 

 

[joe90]

Because of a very high water table where I have built I put a French drain 250mm below floor level around the house and piped it into a ditch nearby, works very well and have had no further damp issues within the soil. It might also be worth checking the rainwater drains run properly away from the house (no soakaway next to the walls).

[Ferdinand]

I would take up one row of pavers and go down first with just a trench and see over winter if that dries it out. Perhaps incline the bottom slightly away from the house.

 

For a membrane I would use something like Wickes heavy duty weed membrane.

 

If it works you could just fill it with river pebbles, or move on to your French drain with a soakway.

[TonyT]

https://www.drainagepipe.co.uk/perforated-filter-drain-pre-wrapped-80mm-o-d-x-50mtr-coil-p-FD8050/?keyword=&matchtype=&device=m&campaign=&gclid=Cj0KCQjw18WKBhCUARIsAFiW7JxMA9BBlnr9PqDx4sHtpMME7Sn1mEWjVn3ph3ut7iBgKN136c6RjBYaAsdZEALw_wcB
 

 

[rh2205]

I guess I’d wrap it myself for that price…

 

https://store.jdpipes.co.uk/80mm-perf-land-drainage-coil-25m/?keyword=&gclid=EAIaIQobChMI48nb5L6f8wIVBoBQBh0BvwhoEAQYBCABEgKb3PD_BwE

[rh2205]

Anyway maybe I’m reading it wrong but a membrane against the wall surface would usually be a bit like a Dpm one, I think sometimes people use dpm paint for french drains against walls though obviously the first option is more robust than those rubbish paints which is why the trench experiment idea might be the first way to go to determine if you can just do a really basic job.

[saveasteading]

29 minutes ago, rh2205 said:

I guess I’d wrap it myself for that price…

Quite right. That price is silly high, presumably only specified by clients that don't thrust the contractor to wrap it properly.

In your case, you can line the trench with it, so that pipe and gravel are enclosed and kept free of roots.

 

to protect the wall from damp you would need another membrane. a roll of dpc would be easy to place.

 

I like these agricultural pipes as they are cheap, fit in the boot, and are cheap. 

If used in a french drain they increase the volume considerably compared to gravel.

 

Handy for soakaways in general.

 

Once the drain is full, the water has to go somewhere. Do you have a slope and a drain or soil nearby?

[Ferdinand]

39 minutes ago, rh2205 said:

I guess I’d wrap it myself for that price…

 

https://store.jdpipes.co.uk/80mm-perf-land-drainage-coil-25m/?keyword=&gclid=EAIaIQobChMI48nb5L6f8wIVBoBQBh0BvwhoEAQYBCABEgKb3PD_BwE

 

I used rigid soil pipe and drilled lots of holes in it. 

[tvrulesme]

3 hours ago, Ferdinand said:

I would take up one row of pavers and go down first with just a trench and see over winter if that dries it out. Perhaps incline the bottom slightly away from the house.

 

For a membrane I would use something like Wickes heavy duty weed membrane.

 

If it works you could just fill it with river pebbles, or move on to your French drain with a soakway.

Great idea thank you. One more query to this. I suspect the answer is no but would I be allowed to connect to this underground which is just outside the boundary of the property? My downpipe already discharges there. I ask because I read "In newer homes the downpipe is taken down into the ground to a direct connection with the sewer pipe, avoiding having open drains around a building"

[rh2205]

No, I mean there’s a chance no one will notice. But otherwise new connections are expensive. The guidance is now all for open drains! Swales, rills whatever that keeps it somewhere so someone can actually see & maintain it & of course delaying entry into the sewer will help reduce pressure on our undersized badly maintained sewers.. but in reality your alteration won’t be perceptible on the impact it causes on the sewer unless you add together every new addition on your entire street ?.

[Jilly]

You could put a water butt there and just send the excess into the storm drain?