ditch rather than french drain

[dtl]

Hello,

Our house is built from field stone with a rubble infill.

Around a single story extension (1900) at the back of our house the ground levels are a few inches higher than the interior concrete floor.
Lowereing the levels of the outside ground is not easy, so some time ago french drains were installed against the exterior all.

These french drains worked well for a while, however they have now become contaminated by soil and the concrete floor is becomimg damp.

Rather then redoing the french drains I think I would prefer to have an open ditch round the perimiter of the exterior of the wall, which will have the benefit of keeping material off the exterior wall.

Has anyone got experince on how to build such a thing, so that it looks reasonable?

Thanks

 

[JohnB]

An Englishman's home is his castle, so a moat is very appropriate :lol:.

Sorry, I'm in a good mood this morning, for once

 

[Flyfisher]

An interesting question, for me at least, as I have a similar thing to tackle.

I'm thinking of two possibilities:

1. Lowering the ground for a distance of about 1 metre from the affected walls and building a retaining wall to hold back the higher ground. Then (probably) gravelling the lowered ground, effectively forming a pathway around the walls that is lower than the internal floor.

2. Digging a narrower trench (say 6-9 inches) next to the walls and then covering the trench with some sort of cast-iron grating.

From what I've read, an open trench will provide better ventilation to the walls than a french drain (which makes sense as the walls are in free air rather than well-drained soil/gravel which will retain some moisture).

The good news is that you already know that the french drain worked. Do you know when they were installed? I'm just curious to know how long they lasted before silting up.

 

[MdB]

Our neighbours have a 100mm to 150mm trench around their house, some of it covered with a grill. Seems to work very well.

 

[robgil]

you could try here.

http://www.pavingexpert.com/cgi-bin/ib3/ikonboard.cgi?s=a881b2677a3b079714ab19a36438e400

 

[Penners]

I agree entirely with Flyfisher's analysis, above. Exposing the walls to a level below the interior floors (at least 150mm if your footing are deep enough) will probably be the best plan.

Just make sure that you don't dig down to, or below, the bottom of the footings. Some old properties have very shallow foundations.

 

[dtl]

My french drains were about 7 years old.

I think I prefer the idea of digging a trench 6-9" wide against exterior wall.

Cast iron grating sounds nice though I am not sure how it would be fixed in position.

I think initially I will install sarking board along the soil sides of the trench, with the upper edge of the sarkimg board just above the old ground level.
I can then see how the drain performs without too much on anything fancy.
Perhaps I could prop slates against the wall supported at the lower end by the top of the sarking board.

 

[Stephen]

I have provided advice on this in the past - look in the Agony Uncle section. In the recent AU answers that are soon to go live I think I included a sketch showing a suggestion of how to do this.

Stephen