# Formed Concrete French Drain?



## Msradell (Sep 1, 2011)

What you're talking about is certainly not a French drain. French drains are trenches or holes filled with gravel to dissipate the water. What you're talking about is basically just a concrete gutter. Actually what the original built is a French drain, it was just put in the wrong place! It's hard to tell from the picture how much slope you have in your yard but a good solution may be too bury corrugated pipe from the end of your gutter. You can run the first 10 feet or so in solid pipe to get away from the house and then use perforated to dissipate the water. You would bury the perforated in a bed of gravel.


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## AllanJ (Nov 24, 2007)

A formed gutter, flush with the surface, usually quite shallow, and usually about a foot or two wide, intended to carry away rain water by gravity without the water being consistently right up against a foundation or curb, *IS* a French drain. It may be molded concrete or it could be constructed of bricks so as to be porous but with the majority of water flowing along rather than soaking in. It gets its name from being used in France.

The underground French drain, or weeping tile system, is named after a person. It, too, is meant to collect water and carry it via gravity elsewhere for example to a dry well or a sump pump. An "underground French drain" with (inlet and) no outlet and whose purpose is to allow water to soak into the ground in all along its length is properly called a leach field even though it may be constructed in the same manner.

If you can find the molded concrete sections, you can lay them along the line you have envisioned, leaving the area between them and the foundation for a garden or whatever. If you can only find straight sections you may be able to lay them around a curve where there is a triangular gap at each joint that you fill with hand mixed concrete (or coarse sand if the gap is very narrow) and you can arrange it so that it still looks good.


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## Msradell (Sep 1, 2011)

AllanJ said:


> A formed gutter, flush with the surface, usually quite shallow, and usually about a foot or two wide, intended to carry away rain water by gravity without the water being consistently right up against a foundation or curb, *IS* a French drain.


Can you please provide me a reference for this. I did some extensive looking to make sure I was correct before posting my post and found nothing that showed a non-permeable surface being used to construct one.


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## AllanJ (Nov 24, 2007)

I can't find the pictures I saw on the Internet some years ago, showing a slighly dished brick "walkway" around a building foundation and used to drain off water falling from the roof, and called a French drain with reference to France. However I found this ditch, not filled with gravel. The appearance of the ditch suggests to me that it is not sealed at the joints.:

http://activerain.com/blogsview/1333940/southern-maryland-real-estate-french-drain-


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## pls8xx (May 2, 2009)

Thunder Chicken,

Some type concrete edge to the planting bed does seem appropriate. And forming a curb as in the example you gave is well within what most DIY people can do. But before I start giving you a method to use, I think you should consider the overall drainage problem. If you don't get the grades right you will not be happy with the result.

What you have described starts as a surface water problem. Subsurface drainage is a bad idea and anything constructed that allows surface water to permeate into the soil is sheer stupidity. French drains have become the biggest scam of the landscape industry.

The first step in determining proper drainage for your property should be to assess the volume of water you have to deal with. This is a function of the size of the area. You should consider all rainfall from roofs and yards, including any area on neighboring properties that flows onto your lot.

It's best to do a plan view drawing of all your property. The drawing should show the location of any water coming onto yours and the size of the up-slope area as can best be determined. For legal considerations, the location of where water leaves your property is also important. In most states you may not block the natural water flow from a higher property, nor may you change the location or character of the flow as it leaves you property.

Adding ground elevations to your base map will then show the route that water takes and any places where the grading is not adequate or desirable for the predicted volume of flow. The elevation at the exit point is paramount to any drainage design, as all grading and any pipes used must be above this elevation. 

A copy of lot survey or public records can be a big head start in creating the base map needed.


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## Msradell (Sep 1, 2011)

AllanJ said:


> ..... However I found this ditch, not filled with gravel. The appearance of the ditch suggests to me that it is not sealed at the joints.:
> 
> http://activerain.com/blogsview/1333940/southern-maryland-real-estate-french-drain-


Even the text with this picture says they are made of gravel and designed to dissipate water into the ground, not really what the picture shows but certainly what they're referring to.


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## Thunder Chicken (May 22, 2011)

The whole idea is to get surface runoff from the lawn and water from the two gutters down around to the downhill side of the house. I want as little of this runoff to actually percolate into the ground in this corner, hence the idea of a surface gutter/French drain (pick whatever term you like and stick with it. I have heard both terms used).

The question is how to construct this gutter/curb thing. I have seen curbing sections, but they are large and straight. I am looking for something that I can get into a curve. I am thinking more along the lines of a formed concrete profile vs. a cobble masonry thing. If I could get a baby version of this thing I would be very happy:

Delta Machine Kerbing


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## Msradell (Sep 1, 2011)

Thunder Chicken said:


> If I could get a baby version of this thing I would be very happy:
> 
> Delta Machine Kerbing


That one is the baby, here's the daddy: http://www.youtube.com/watch?v=85dTYvtDiWM

Actually there are companies that have small machines that normally use them to make curbs for flower beds etc. maybe one of them could do what you want very easily?


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## pls8xx (May 2, 2009)

First, you will want to select a curb profile. Things you should consider:

1. Your project will probably use less than 1 cu yd of concrete and most ready mix suppliers will have a minimum order way over what you need. Site mixing concrete is a lot of work. You want a design that minimizes the amount needed.

2. Most homeowners are not accomplished at finishing concrete. Because the curb will be curved, I suggest you keep the profile to straight lines.

3. Keep the minimum depth of concrete to 4 inches.

One such profile might be 7" high on the back side and 5 inches on the front, 10inches wide, shaped like this:










I assume you will put the high side of the curb toward the house?

I need to know the length of the curb and the amount of vertical drop from start to end.


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## pls8xx (May 2, 2009)

DIY curb is not that hard to do. A homeowner doesn't have the tools or equipment that a contractor has, but alternate methods are available.

Forming is basically two runs of a bendable material for the front and back of the curb such as quarter inch plywood. Curves complicate the forming because plywood can be bent in only one direction. It is desirable for the curb to have a uniform downward slope. Since plywood can only be bent to a plane surface, forcing a uniform slope on curves causes a twist to the formwork, the magnitude depending on the terrain slopes. Sometimes this effect is so minimal it can be ignored. Where necessary, a number of methods can be used to overcome the problem. A detailed plan is needed to produce a suitable result.


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## Thunder Chicken (May 22, 2011)

Well, I finally made some progress with this. I shoveled out all of the stone and backfilled with good soil from a high spot in the yard. After a lot of fussing and grading I managed to get a subtle swale to slope away from the house and run around the corner of the house. I seeded and put some burlap down to keep the seed in place. I think I'll wait for things to settle down and for the grass to come up before I decide on any concrete work.

One part is still an issue, the part of the house on the piers to the left and behind the chimney. This is too close to the ground for me to fill it in underneath with soil. I banked up the earth under the drip line so the slope goes away from the house and seeded it over, but that isn't going to last forever. I'm thinking that maybe I could put in a concrete "curb", with the top flush with the grade, between the pier and the foundation on either side. I could then fill in under that section of the house behind the curb with some clean stone. Any better ideas?


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## AllanJ (Nov 24, 2007)

Wherever you have a bed or channel filled with stone or gravel, water will remain there until it soaks into the soil unless a channel of the same or greater depth (can also be filled with gravel) or a drain pipe continues from there and then downhill to a final destination for the water.

Sump pumps are used when the water runs out of downhill before it reaches the final destination.


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## Thunder Chicken (May 22, 2011)

AllanJ said:


> Wherever you have a bed or channel filled with stone or gravel, water will remain there until it soaks into the soil unless a channel of the same or greater depth (can also be filled with gravel) or a drain pipe continues from there and then downhill to a final destination for the water.
> 
> Sump pumps are used when the water runs out of downhill before it reaches the final destination.


That's exactly why I am doing this. One of the previous owners dug out a trench right next to the foundation and filled it with stone. 

The grade as indicated has a channel that goes downhill to the backside of the house (the low side). I'm assuming a good bit of the water will insoak in the swale, but at least it is several feet away from the house now. If I can get some grass to grow there that will help soak up some of that water, too.


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## House Engineer (Feb 23, 2012)

It is really cool to see that you plan to use such a well-conceived solution to the backyard drainage. I see many people suffer with chronic basement flooding because they do not recognize the need for a repair like yours.

Another helpful thing you can do is to grade the surface to slope a little, away from the house. Then install a 4-6 foot wide polyvinyl plastic sheet under that gravel located up against the house.

And install a 10-foot long downspout diverter to drain the downspout away from the house. (or hook the downspout up to your new drainage system).


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## Thunder Chicken (May 22, 2011)

House Engineer said:


> It is really cool to see that you plan to use such a well-conceived solution to the backyard drainage. I see many people suffer with chronic basement flooding because they do not recognize the need for a repair like yours.
> 
> Another helpful thing you can do is to grade the surface to slope a little, away from the house. Then install a 4-6 foot wide polyvinyl plastic sheet under that gravel located up against the house.
> 
> And install a 10-foot long downspout diverter to drain the downspout away from the house. (or hook the downspout up to your new drainage system).


All of the gravel has been removed and replaced with compacted fill and topsoil and overseeded with grass. I actually did install a temporary diverter to my downspouts to route water down to the backside of the house until the seed sets.

The slope of the rest of the yard (the yard under my feet when I took the photos) had TWO concrete patios buried underneath it. Someone years ago wanted a patio and poured one, then a subsequent owner didn't like it and buried it, then another owner wanted a patio and poured a new one, and yet another owner didn't like that one and buried it again (so it was soil/concrete/soil/concrete/soil, like a layer cake). I sorta wished concrete mix was more expensive so people thought before the built, but what are you going to do? Anyway, I had all of the concrete dug up and regraded, so the level of the yard dropped over 9 inches. It still is a bit high, but I can't lower it much more without it becoming lower than the neighbor's yard.

A french drain is still an option (and an easier one now that all of the concrete is gone and the grading makes its location easier to set). I want to see how things settle out after the grass sets. Things are already much improved now that I don't have a swimming pool right up against the foundation. The crawlspace was amazingly dry regardless of the previous bad grading, and I want to keep it that way.


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