Best way to proceed with French Drain on old stone house?

10 years ago

Hi, IÃ¯Â¿Â½m new to the forum and am hoping that someone on here will be able to help me.

I have a 2 story house which is built into the side of a hill. As you approach the house from the road, you are presented with the 1st floor, and so it looks like a bungalow. However, there is a floor below which on the road side of the house is Ã¯Â¿Â½buriedÃ¯Â¿Â½ underground. The house is built from 2 skins of stone Ã¯Â¿Â½ itÃ¯Â¿Â½s a couple of hundred years old.

My plan was to make a French drain along this front wall (and down the side of the house) down to the level of the floor downstairs. I have (with help) dug the trench, but am now wondering whether this is the best thing to do, given that the walls are stone, and as I understand, need to Ã¯Â¿Â½breathÃ¯Â¿Â½. My plan was to render the outside wall so that there is a smooth surface on which to place a membrane and then put the requisite pipe-with-holes at the foot of the trench and refill with gravel and soil.

This should stop moisture from the earth penetrating the house, shouldnÃ¯Â¿Â½t it? But what will happen to moisture on the inside which is trying to Ã¯Â¿Â½escapeÃ¯Â¿Â½? Will it hit the membrane and come back inside, creating damp?

Thanks for taking the time to read this, and let me know if you need any more info. Hopefully someone will have a decent solution!

Cheers, Paul

Here are some pictures:

http://s1278.photobucket.com/user/paul_matthews3/library/French%20Drain

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Comments (4)

kitasei
10 years ago
I am not an expert but I can give you my experience with a stone house partially below grade, on which we are right now having footing and curtain drains re-done. We are using the best contractor for the job in our area, and he insisted on doing it this way. The trench must be dug at least a foot below the foundation. Two drains will be installed - one without holes to take the water from the gutter leaders and one with holes to carry off surface and ground water. The stone wall that is underground was power washed, re-cemented, and tomorrow will be sprayed with a rubber sealant So far everything I've said I'm sure you already know. But where I think he departs from common practice is in removing all of the rocks and stones against that wall and replacing it with clean fill. Rock retains moisture, which gets wicked into your house through the stone of your foundation. You can help the dirt to dry out faster by eliminating foundation plantings and exposing it to sun (also shows off your stone wall better!). Roots are also conduits for water and can penetrate the wall. Pay attention to the depth of your drain - if it's not BELOW the foundation, you may be wasting your time.
Now as for the question of moisture inside the house - my own guess is that it will have plenty of other opportunities to escape through the rest of your walls that are not underground. You are always going to have a problem with condensation because of the temperature differences between the stone and air (especially in hot humid summers), and may want to use a dehumidier or fan then. I will be interested to hear others' thoughts on all of this.
worthy
10 years ago
The trench must be dug at least a foot below the foundation.

Good grief!

That's the best way I know to undermine a foundation. I've seen it done, just before the whole project was red flagged by the building inspector. That's why in new home construction weepers go beside the footings, not below them.

(Your URL doesn't work.)

Here is a link that might be useful: Cure for a Leaky Stone Foundation--An interior approach

This post was edited by worthy on Thu, Sep 19, 13 at 9:17
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vjrnts
10 years ago
The URL works fine if you take the space out before the "n" in "drain."

Here is a link that might be useful: Pictures
kitasei
10 years ago
yikes, Worthy, please tell me more about the problem of undermining the foundation because the excavator sure did take out a mountain or rocks partially under our slab.. Do I call the local inspector?