Author Topic: Yard sloping towards house: French drain? Swale?  (Read 426 times)

Poundwise

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Yard sloping towards house: French drain? Swale?
« on: April 07, 2019, 05:47:42 PM »
Our house sits sideways on a small granite cliff. Our side yard, which we recently excavated about a foot down to the rock because of contaminated soil, slopes downward to the house.  The runoff is probably is the source of water in our crawlspace. We'd like to level off the area and build raised vegetable beds there, and also improve drainage while we're at it.

Our idea was to use retaining wall block to build a 8' x 16' rectangle parallel to the house, fourteen feet away from the foundation. We would fill this rectangle until the surface was level. Not sure yet whether we would use gravel and pavers (for raised patio space), gravel and soil (plant directly in the soil),  or plain gravel (put raised garden beds on top).  This would probably be a DIY project.

The question is, what would be best for drainage?  Would filling with soil be best?  Or would a level paved surface be better?  Would placing a perforated pipe along the base of the lower retaining wall direct the water sideways into our front yard?

soccerluvof4

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Re: Yard sloping towards house: French drain? Swale?
« Reply #1 on: April 08, 2019, 06:38:37 AM »
what is your the ground/Soil made up of below the level of your crawl space. Also if you use a perforated pipe make sure use one that has is the sock type other wise the holes just get plugged up. You'd be better of filling up with as much gravel as u can below the level of the crawl space and have pipe run through gravel at that level and drain out which means you would need to have some pitch. Personally I would tie in a couple of french square box drains at the top or one long thinner one with a swale. That way you can always pop the cover and clean the drain and I would use all PVC then for all the drainage instead of perforated pipe.

Poundwise

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Re: Yard sloping towards house: French drain? Swale?
« Reply #2 on: April 08, 2019, 10:43:28 AM »
Thanks, @soccerluvof4! I'll look up "french square box drains". 

It's all solid rock under the crawl space.  Basically, we're on a big tilted rock. The side yard is at the top of the rock, then comes the house, and the crawlspace/garage happens in the wedge shaped area between the rock and house. Rainwater seems to flow down the surface of the rock, under the house, and into the crawl space. There's a sump pump at the bottom of the crawl space but it's still mighty damp in there unless we run a dehumidifier constantly. I was hoping that we might be able to redirect half of the water before it even gets under the house.  We can't block the water at the house, because we would have to rip up our deck to access that area.

I'd be building two retaining walls between the top of the rock slope and our house. My idea would be to redirect the water flowing down from the top of the slope 90 degrees, parallel to the retaining walls, so that it so that it goes to our front yard instead of under our house. Then we have to diffuse the water some how. 

It would be kind of like an underground gutter. 



Poundwise

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Re: Yard sloping towards house: French drain? Swale?
« Reply #3 on: April 08, 2019, 10:57:05 AM »
While googling "french square box drains" found this very helpful discussion of drainage!

https://www.tlake.com/blog/french-drain-vs.-trench-drain-vs.-swale

soccerluvof4

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Re: Yard sloping towards house: French drain? Swale?
« Reply #4 on: April 08, 2019, 02:58:08 PM »
If you get a chance send a photo or two. I owned a landscaping business for years so If i saw the problem I might be able to come up with some options for ya. Can always pm them if you want too. There is always a fix. Like anything though doing what makes the most sense and not breaking the bank.

Poundwise

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Re: Yard sloping towards house: French drain? Swale?
« Reply #5 on: April 08, 2019, 03:27:38 PM »
Gee, thanks!  I'll send you a PM later with a photo.