Putting In French Drains

[MMH]

I have approximately 500' of french drains to put in around a pole barn that I just built & the driveway that runs into it. I was going to dig the trenches 3' to 4' deep, put in a little bit of B3 gravel, drop in a 4" drain pipe, then fill up w/ B3 gravel. The reason that I was going to go that deep was to make sure that they would drain even in winter & not freeze. However, I noticed that the drains around my house are just one foot below the surface, So, is going 3' plus deep for the trench depth overkill? How do the drains that are only 1' foot below the surface not freeze in winter? I am in western PA and winter is plenty cold & long.

 

[TBarD]

Seems like overkill to me - there shouldn't be any drainage issue anyway if it is frozen out. BTW I just looked into this for a french drain around a pole barn myself, and ended up going with a product called Multi-Flow. I haven't installed it yet so can't report on how well it works (still doing site prep for the barn), but the issue is that a conventional french drain tends to silt up and clog over time. If you do a conventional drain pipe in a trench it may help to add some geotextile fabric to help prevent silting up.

 

[DJ54]

The 1' deep french drains were probably put in to handle the wet weather run off. Around here in the spring, you'll find wet springs down about 18 to 24" in this shaley clay.

If you're worried about freezing, find out where the frost line is for your area. Here (central Ohio), they say it 36". And that would be an extreme condition, of bare ground, with no snow cover.

You'll proably have more problems on the outlet end with freezing, than in the trench. And if draining into a deep swail or hollow, it will take longer to thaw there, depending on how much sun it gets.

 

[vtsnowedin]

A lot depends on your soil type. If your in sandy soil a french drain is just a hole full of course rocks that hold the run off long enough for it to soak into the surronding soil. If you have a clay or rock base that won't absorbe soil at a decent rate you need to trench it off to a point where you can daylight it into a ditch etc. I find that fabrics often plug up in clay soils and do more harm then good. (Lots of varied opinion on that of course) Here in Vermont we run underdrains down six feet to get below frost in snowplowed areas and backfill around the pipe with ether 3/4 clean stone or clean sharp sand and fill the trench all the way to the top with clean free draining material. A top dressing of 3/4 stone along the eve line of a building about a foot deep works well at the high end of the building with the trench pitched to drain getting deeper as it goes around the building then off to the outlet point. 1/4 inch per foot or better to flow well.

 

[Gator6x4]

I have approximately 500' of french drains to put in around a pole barn that I just built & the driveway that runs into it. I was going to dig the trenches 3' to 4' deep, put in a little bit of B3 gravel, drop in a 4" drain pipe, then fill up w/ B3 gravel. The reason that I was going to go that deep was to make sure that they would drain even in winter & not freeze. However, I noticed that the drains around my house are just one foot below the surface, So, is going 3' plus deep for the trench depth overkill? How do the drains that are only 1' foot below the surface not freeze in winter? I am in western PA and winter is plenty cold & long.

Not for water lines or french drains. This article addresses piers and foundations. Scroll down to the bottom and located your county of residence and you will see the reccommended depth placement to prevent freezing. I am sure it would have to equal or exceed for water.http://www.engr.psu.edu/phrc/pubs\TB0101.pdf

 

[s219]

What are the soil conditions? If you go 3' deep, can you even drain to daylight if you need to?

I ran my french drains about 1' deep. The trench was lined with septic paper, bottom filled with #57 gravel, then the 4" punched pipe with holes on the bottom, then more gravel. At the top, the septic paper was folded over on itself, then the trench was filled over with topsoil. This was done 12 years ago, and they still work very well. We needed them because our house is midway on a slight hill, and the drains intercept runnoff and divert it around the house.

The drains are connected to 4" solid pipe that joins pipe from my downspouts and directs outflow to the back yard where there is a pond. There are 4 downspoints and three french drains dumping into two main runs to the back yard.

The only problem I have had is Willow roots running up the outlet of the drain pipe in the back yard and clogging it up. I don't ever notice until a hurricane hits and my wife asks why the front yard is a lake. Twice now, I have run out in the middle of the storm, used vice-grips to get a hold of the roots, and pulled out a 10-12 foot long "snake" of roots that has perfectly formed to the shape of the corrugated pipe. Looks like a pre-historic serpent. When I cleared it last fall during Hurricane Irene, the water shot out so fast it turned into a geyser. That's what 8-10 feet of pressure head will do. Next time, I hope to remember to clear the roots before the storm...

One year we had muskrats living in the pipe, but I imagine the willow roots won that battle, since I haven't seen muskrats in a long time.

 

[boggen]

the corrugated pipe / hose with holes in it. vs sch40 pipe with holes / slots in it. the corrugated pipe / hose will more likely last long and handle freeze / thaw movement of the ground better. due to the stuff being more flexible.

with your statement of all around the entire shed/barn. sounds strange. like you built shed in the lowest area possible. and did not build the area up some before putting the shed in. so the ground would slope away from the shed. this removing a good amount of run off water away from the shed.

every situation is different. but good landscaping and shaping the land can go a very long ways. in help dealing with freeze / thaw and in that ground movement.

 

[Fossil Farm]

As was mentioned, the first concern is if you have an outlet for the tile. The tile needs a minimum of 1 inch for every 100 feet, preferably a bit more if installed by backhoe or by hand. Will you have gutters and downspouts on the barn? Will the floor be gravel or concrete? If concrete, and depending on the size of the barn, you may also want a line or two on the interior to keep any stray subsurface water from underneath the slab. You do not have to go deep, because you are moving free water out before it freezes, but a couple feet deep would be better if you have a clay or silty clay soil and have a proper outlet for the tile. Bank run gravel has worked better around here because there are many fines in the limestone we get from the quarry and can tend to seal over the tile in some cases. Doesn't happen often, but if bank run is available, it tends to work better. Good luck.

 

[MMH]

I guess additional details are in order. My house and pole barn are about 2/3 of a way up a hill. I had to do a lot of land clearing and excavating to create the flat area for the pole barn and parking area. I cleared an area that was 60' wide & 100' long for the pole barn and an area that was 50' by 40' for the parking area. The pole barn is only 40' by 60' but there additional area cleared around the building. I ended up cutting into the high side of the hill by 7' & the low side was built up by 5'. It's not exactly as flat in western PA as it is in Kansas. As far as the outlet for the french drain, I believe that the creek that I will be day-lighting into is about 100' feet away with a 30' drop from the pole barn, so I think that I will be OK in that area.

 

[vtsnowedin]

Does the surface water from the top of the hill run down and over the 7 ft cut slope towards the building? If it does you should dig a diversion ditch at the top of the slope to direct the water off to the lower side before it gets to your cut.
Weeping willows within a mile of a septic system need to be pruned off six inches above the ground and have the stump soaked in Roundup.
Fossil Farm. ? You must have a very good pipe laying crew with a good laser to hold just one inch in a hundred feet. I'd go with at least 6" and a foot or two would be better. Typo perhaps ?