French Ditch

[Knight9]

We just built a new house on our 10 acre parcel of land. We are very happy with the house, with the exception of one thing. We built on a fairly high spot of the land, but the builder's foundation sub dug the basement I would say about 1-2 feet too deep. Thus although I am not concerned about runoff on the front of the house, it is my greatest concern on the backside.

There is about a 1-2 foot slope that runs towards the house. The land is all clay in the close proximity of the house as I have not done any landscaping yet. This spring we will be doing our lawn, planting trees and all the rest of that good stuff. So let me get to the point of my question...../w3tcompact/icons/smile.gif

I am thinking about running a french ditch parallel with the back of the house to funnel all the water away from the foundation. The question is, do you have to have some sort of exposed aggregate (ie gravel or whatever) open on top of your perforated pipe so water can percolate down, or can you cover the gravel with dirt and plant grass?? If you plant grass, does the ditch still function and funnel water away, or should I just plan on having a strip of rock passing through my yard? If I need exposed rock to allow the water to penetrate down into the pipe, then I guess I would probably just try and do some sort of gravel "pathway" that would allow the french ditch to double as a sidewalk. Not sure how that would look.

Any ideas or suggestions? Something I could do other than a french ditch??

Thanks,
Kevin

 

[MarkV]

Kevin, I can understand your concern. Is it unrealistic to regrade the back area so that the slope will be away from the house? Even if the grade could be dropped to what we call a swale to divert water away from the foundation. What I call a swale, is a very shallow wide ditch planted to match the rest of the yard. We often have to use this type of system when building houses in the city. To me the problem with a French drain/ditch is that in heavy run off it will not be able to keep up with the flow. Keep us up on what you do.

MarkV

 

[mdbarb]

You'll need to grade a slope away from your house for a couple feet. At that newly created swale dig a ditch at least as deep as the lowest part of your foundation, lay in filter fabric, lay a 4" perforated pipe on top of the fabric at the bottom of the ditch, fill the ditch almost up with drain rock, fold the filter fabric over the gravel to envelope it and top off the last 8-10 inches with topsoil, plant and enjoy...

 

[Henry]

I've had to deal with similar drainage situations in several different situations, including areas that have really nasty clay soils (Cental PA). Here's what we've done in the past:

Generally, you don't need exposed aggregate with a French Drain system. I've dug the ditch for the french-drain pipe about a foot deep. Put in about 1" a aggregate, then the pipe, then a few more inches of aggregate. Top it off with a nice 3-4" layer of topsoil or sod. If you can work-in a bark-chip bed around the house and just top things off with chips, versus soil that works great too !

In terms of grading. I've used two techniques:

In one situation, we just sloped the soil back from the house to a low point about 6 feet out from the foundation ... maybe a total of a 6" drop. (which is where we laid the french drain-pipe).

In another situation, where we had to deal with a bad slope and rain run-off from a large roof w/no gutters. We used the same basic sloping technique as described above, but we also laid-in a layer of heavy plastic that went from the foundation then out 6 feet to the french-drain ditch, covered the plastic with aggregate and bark chips on top. It looked great and solved a major problem with a wet crawl space under the house to boot !

I now live in Florida, and have a whole new set of drainage & soil problems. With everything so dag-gone flat, you have to be really careful with drainage... especially when you get a good Florida style down pour (e.g. 5+ inches)! When you lay french-drain in Florida it's a good idea to put a sand-sleeve around the French-Drain pipe. The sleeve is made from that back matte material that you use for weed protection in the garden.... It helps keep the sand from filling up your drain pipes ....

Good luck with your drainage project!
Henry

 

[Knight9]

No problems with the water getting down through the top 8-10 inches of dirt/grass into the rock and finally the pipe?? My concern is that the water would just lay on top of the grass.

Kevin

 

[Knight9]

Henry,

I really like the idea of burying the french ditch under chips as part of a bed around the house. We were planning on putting some low shrubs and other items around there, so that just might be the ticket!!! Excellent idea.

Thank you for the input.
Kevin

 

[Boots]

Kevin,

If it's mostly surface water that you're concerned about, you may not need the French drain.

A friend of mine had the same exact issue with a lawn that forced surface water toward his house. The way he fixed this problem was to put a small shallow swale about 2 feet from the edge of the house and installed an underground PVC pipe (4 or 6") under this swale with a couple of drop inlets. The drop inlets were homeade from the square type of concrete blocks, some bags of concrete mix and a piece of industrial grating over the top. The PVC is not perforated at all, and takes the surface water around to the back side of the house to an open drainage ditch. This way you can lay sod right up to the house and not have any unsightly gravel exposed.

Take Care,
Boots.

 

[Knight9]

Boots,

Thank you for the input. That is a very useable idea also. It is just surface water that I am worried about. I do have a slight slope away from the house, but even in the light rain that we had last fall I ended up with large pools of water (6 feet across by about 2-4" deep) on the surface about 6-8 feet away from the house. I am just concerned that with heavy rain or significant spring run off the water pools would get large enough to run up against the house. I could certainly put in some "surface drain holes" that would funnel the water down into a PVC pipe running under the ground. Not sure how the concrete block thing would work...I'd have to do some pondering on that.

I suppose there may even be commercially available products that have some sort of kit that would allow the homeowner to put in vertical drains into horizontal drainage pipes. Anyone ever come across such a thing??

Thanks again for the input.
Kevin

 

[gerard]

I've seen grated drain tops like you're looking for at Home Depot, shouldn't be too hard to track down. Put a few right in the center of where you're biggest puddles are and that should solve your problem. This will work IF the problem is only surface water runnoff. A slight regrading would be even better but without knowing your layout I don't know if thats feasible. The nice thing about a proper grading or swale is it can take a much larger volume of water away a lot faster than a 4 inch pipe. In a heavy rain the water shed by the roof can be PRETTY large.

 

[Wingnut]

Kevin ... just gotta say you're a brave man wanting to build a french anything in Alberta!

pete

too bad that common sense ain't