Freezing french drain...

[Ernest T. Bass]

Hi all,

We have a "rubble trench" foundation under our home, with a drain at the bottom that runs out to daylight. Or, in our case, -20 degree temperatures in the winter. Last year it froze solid at the end, and I had to dig it out and cover it with straw. I've never read about protecting the end of the drain from freezing, but apparently you have to.. Would digging it back to about 2 ft. deep, covering it in gravel, putting a layer of foam board over it and filling it back up with dirt do the trick?

[glenn kangiser]

That is kind of a hard one.  The only thing keeping it warm is the earth - if it freezes the water will freeze.  Possibly you could get a drop and or flare at the end to a trench so it can run free.

[JRR]

Sounds like the drain-end is freezing due to its exposure to air.  I like the plan you described.

Did the covering of straw help?  Maybe a tarp protected covering of straw would be an easier fix ... but one you would have to tend to yearly.

[Ernest T. Bass]

Yes, we'd like a permanent solution.. Glenn, what do you mean by a flare to a trench?

[peter nap]

I expect a cold frame type of cover would solve the problem. What length are you talking about?

[John Raabe]

How about having the drain end in a dry well? This may not have the capacity needed for a really large water flow, but a dry well is often something like a buried steel drum filled with broken rock or concrete with an open bottom and or holes drilled in the sides. The whole thing is buried below frostline and the footing drains and downspouts can drain into it for dispersal into the soil.

[glenn kangiser]

Yes, we'd like a permanent solution.. Glenn, what do you mean by a flare to a trench?

Not even sure if it would work in your situation but just widening it out so there is more room for the water to spread in a lower area without blocking up in front of the pipe and making an ice dam.

John's dry well seems like the best idea if its big and deep enough.

[Ernest T. Bass]

I expect a cold frame type of cover would solve the problem. What length are you talking about?

The drain comes out of a fairly steep hill, and the pipe travels into it for about 10 ft. before it's below the frost line.

I guess the dry well idea is kind of what I was talking about, though, instead of a buried drum we would just make a pocket of drainage gravel for the water to disperse in. It would be easier if we didn't have to dig all the way back to below the frost line, though. That's why I was asking about the insulation.

[glenn kangiser]

If you didn't mind landscaping you could put an earth mound over it to raise the bottom of the frost line - then like the rest of the world in your area, the frost would still only go to that depth and the soil would be your insulation.  

You could just put your rock layer down under it and some of the geotextile fabric or a heavy layer of straw to keep the soil from filling your rock.  If doig it by hand it could be a real chore, but if machinery is available it could be easy.

[Ernest T. Bass]

Well, we're going to have to get a backhoe out here one of these days to dig a root cellar, so perhaps we can take care of the drain then. Thanks for the help!

[glenn kangiser]

No problem -- keep us posted.

[JRR]

Since you've got some digging equipment available, you may want to add some drain trenches to keep water away from the foundation in the first place.

Fine Homebuilding (Sept, 2007) has an article entitled "Keep your basement dry with a Curtain Drain".  May be worth your reading.

[Ernest_T._Bass]

Our rubble trench foundation is nothing BUT a drainage trench, 32'' wide and 4' deep.  

[glenn-k]

Our rubble trench foundation is nothing BUT a drainage trench, 32'' wide and 4' deep.  

That sounds like a great way to do it.  Sometimes a rubble trench footing can mean rubble - rocks etc with a slurry poured over and into them to make solid rubble concrete.  I assume yours is loose un-mortared,  That is a good way to do it.

[Ernest_T._Bass]

Yes, and we have our footer or "grade beam" sitting up on the surface. It can be a very economical foundation for massive houses if you can get the rock fill cheap enough. Unfortunately, we ended up having to truck it in from over an hour away... Perhaps a more shallow, frost-protected foundation would have been cheaper in our situation.