# Driving the frost deeper?



## K2 (Jul 8, 2005)

With -10 f and the plumbers working overtime, I was thinking about the frost line and some input from the cold weather guys about the frost line. I assume that dry soil is less likely to freeze deep than saturated soil. Also I think that a foot of snow will protect the soil better from freezing deeper. But the rumor that vehichular traffic will drive the frost or that freeze/thaw will drive frost, I'm not quite sure about. Any opinions?


----------



## Redneckpete (Feb 22, 2008)

Any insulation helps. A bit of straw, snow and even a healthy lawn growing over the area makes a huge difference. If you spread 6" of straw over the area early in the season and spread a tarp over that, the area will probably never freeze all winter.

Areas where the snow is removed (roads, driveways, walkways) will freeze much deeper. It is not uncommon for a driveway to have two or three feet of frost under it while the snow covered lawn six feet away remains unfrozen.

Dry soil freezes less then wet soil. Fluffed up soil freezes less then compacted soil. Sandy soil freezes less then clay. Rock (shale or limestone) doesn't really freeze at all.

I never believed that vehicles driving sent the frost down deeper. I always chalked it up to the snow being removed from areas that vehicles drove. I'm not so sure anymore. I've seen frost so deep under roads that I can't explain it.

Lastly, keeping frost out is way easier then removing it once it's there.

Pete


----------



## dakzaag (Jan 6, 2009)

Snow insulates very well. Traffic compresses the snow, removing the air and eliminating the R value. Traffic itself probably doesn't physically push the frost, but the lack of snow would deffinately allow more frost penetration. 

I think that traffic can be blamed on deeper frost because high traffic areas are general snow free except for storm situations.

Right now the ground under all this snow is not experiencing negative temperatures. The roads that are clear are exposed to the temp.


----------



## K2 (Jul 8, 2005)

Thanks, so i'll ask this question. We had 2 days of sub zero but today will be 40*f. Would you think the frost could continue to go deeper regardless of the above ground temps?? I have a property with a shallow service that I am moderatly concerned about. We've had these temps in past years but never without significant snow cover.


----------



## dakzaag (Jan 6, 2009)

Thats a really interesting question, because it doesn't seem logical that frost would continue to "grow" after it warms up. Surely the slow freeze of the soil would stop when there is no more push from above. 

Just from my own experience, I have had several situations where I went through the worst of the cold weather (20 to 30 below zero actual temps) without any concerns and then when a heat wave of above freezing temps would roll in, all of a sudden your dealing with a hydrant or supply line that won't function because of frost. Maybe we let our guard down when it warms up and forget to keep the small light on in a well pit or unplug a heater that keeps a livestock water from freezing up. 

I am not sure why this is, but one time I was talking to a guy who was well into his 70's and he told me to be carefull cause when it warms up, you find yourself with more problems. Up until then, I just figured it was my frustration or imagination that I was having more problems when it warmed up, but his comment has stuck with me to this day. I can't really explain the reason, but now I wait for several weeks of above freezing weather before I stop taking precautions in a vulnerable situation.


----------



## cleveman (Dec 28, 2007)

I always thought that dry soil freezes worse than wet soil because the wet soil is more dense. I based this on the fact that the frost is worst under roads. However, these roads are always cleared of snow, and the ditches are full.

I'm afraid I need to update my thought because the insulation in the ditches is more important than the road being dry and the ditch being wet.


----------



## Tscarborough (Feb 25, 2006)

Dry soil insulates better than wet soil, and when things begin to thaw, the problems that developed under freeze become apparent.


----------



## Jackpine Savage (Dec 27, 2010)

K2 said:


> With -10 f and the plumbers working overtime, I was thinking about the frost line and some input from the cold weather guys about the frost line. I assume that dry soil is less likely to freeze deep than saturated soil. Also I think that a foot of snow will protect the soil better from freezing deeper. But the rumor that vehichular traffic will drive the frost or that freeze/thaw will drive frost, I'm not quite sure about. Any opinions?


I was skeptical about the theory that vehicular traffic drives frost too, but seemingly it's true. 

We had a pipeline being built round here last winter. They take advantage of winter to make access roads across wetlands. They actually hire trucks to do nothing but drive back and forth on the roads to drive the frost down so they can get heavy equipment in there. Don't think they'd spend the money if it wasn't true.

A foot of snow does wonders. The ground will actually thaw if you get enough snow on it. It's all about trapping geothermal heat.


----------



## woodchuck2 (Feb 27, 2008)

Driving on soil definitely drives the frost down further. Several yrs ago before i got divorced i began installing an outdoor wood boiler at my home. Problem was i could not afford the insulated pipe until mid winter. I had no issues digging next to the foundation and dug about 10' until where my ex-wife was parking her car and then i hit about 12" of frost. So i went to the boiler and began digging towards the house. The frost in the middle of the yard was about 3" but when i reached the location of where i parked my truck "next to the ex-wifes van" all the sudden i was hitting over 12" of frost again. I put down calcium chloride with hay over it and i put a salamander in the ditch and i still could not loosen the frost, it was too thick for my mini-ex. The only place in the whole yard where there was heavy frost was where the vehicles were driven and parked. The yard is also very dry and sandy/loose soil so i do not believe moisture was a facter.


----------



## Sar-Con (Jun 23, 2010)

Frost is always deeper under traffic areas. Mentioned earlier, it has something to do with the density of soil. The less dense soil is more laden with air, which provides some insulating properties that slows frost advancement.


----------



## K2 (Jul 8, 2005)

dakzaag said:


> Thats a really interesting question, because it doesn't seem logical that frost would continue to "grow" after it warms up. Surely the slow freeze of the soil would stop when there is no more push from above.
> 
> Just from my own experience, I have had several situations where I went through the worst of the cold weather (20 to 30 below zero actual temps) without any concerns and then when a heat wave of above freezing temps would roll in, all of a sudden your dealing with a hydrant or supply line that won't function because of frost. Maybe we let our guard down when it warms up and forget to keep the small light on in a well pit or unplug a heater that keeps a livestock water from freezing up.
> 
> I am not sure why this is, but one time I was talking to a guy who was well into his 70's and he told me to be carefull cause when it warms up, you find yourself with more problems. Up until then, I just figured it was my frustration or imagination that I was having more problems when it warmed up, but his comment has stuck with me to this day. I can't really explain the reason, but now I wait for several weeks of above freezing weather before I stop taking precautions in a vulnerable situation.


I wonder if it would be safe to say that once the frost is in the ground than it continues to drive deeper regardless of the the above ground temps? We know that gravity moves cold air to the lower position, maybe it could be the same for the earth. Then as you said, we let our guard down. 

Well the plumbers and flood restoration guys are busy around here and may be busy for a while as some of these above ground pipes begin to thaw and shallow pipes freeze.. As I mentioned, we've had these temps in the past but never without significant snow cover. I've found in the past that snow cover up against a building can help insulate and maybe more importantly keep the wind from blowing through and freezing pipes at those tiny cracks like at the sill plate. Thanks!


----------



## Tinstaafl (Jan 6, 2008)

K2 said:


> I wonder if it would be safe to say that once the frost is in the ground than it continues to drive deeper regardless of the the above ground temps?


Yes, though for how long and how deep are questions you'd need one of those pocket protector guys to answer.

Say for example that it's been cold enough that the soil 1' down is frozen to 20°.

The weather warms up to 40°, and the surface soil slowly begins absorbing some of that warmth. Now you have a "sandwich" of frozen earth between two layers of unfrozen material. That frozen layer is going to be absorbing heat from both above and below until it reaches equilibrium, so yes, the area directly beneath that frozen layer will continue to lose heat even though the air is warmer.


----------

