# Do all buildings need to be built below the frost line? (structural question)



## TheWagonmaster (12 mo ago)

I live in the northern US, and I've noticed that some buildings up here don't have a basement. My employer's building, for instance, has no basement. Many cabins are also basement-less, and of course manufactured homes also "sit" on top of the soil.

I was under the impression that all buildings needed to be built below the frost line for structural stability. What am I missing here? Are these people taking a gamble that their buildings will deteriorate more quickly?


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## Tinstaafl (Jan 6, 2008)

If the structure has enough strength and stability that it can do without good support under one or more corner/edge, the only downside of going without a foundation is that the whole thing may tilt out of level as freezes come and go. Sort of like a child's building block sitting on Jello.

If it's not that solid (and most structures of any size aren't), frost heave can cause all sorts of racking and distortion. Obviously, good foundations are best practice.


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## KermieB (Jul 27, 2012)

YES


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## G&Co. (Jul 29, 2020)

You misconstrue the meaning of the word "building".
It is the foundation part of the building that needs to go to frost line. You can have an SOG (slab on grade) building in a freezing climate as long as the foundation it sits on goes to frost line. 
You can also have a frost protected shallow foundation that doesn't go to the frost depth.


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## Stunt Carpenter (Dec 31, 2011)

Just because it doesn’t have a basement doesn’t mean the fondation isn’t below the frost line. For example the garage I am starting next week will have fondation walls down 4ft with a slab poured between


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## We Fix Houses (Aug 15, 2007)

I've asked both these guys the same question --- in Maine and N. Vermont -- dozens of bldgs on grade.


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## TheWagonmaster (12 mo ago)

Stunt Carpenter said:


> Just because it doesn’t have a basement doesn’t mean the fondation isn’t below the frost line. For example the garage I am starting next week will have fondation walls down 4ft with a slab poured between


So do you think it's reasonable to assume my employer's building is post & beam?


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## Stunt Carpenter (Dec 31, 2011)

TheWagonmaster said:


> So do you think it's reasonable to assume my employer's building is post & beam?


No post and beam is an entirely different thing 

what do you do in the trades?


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## hdavis (Feb 14, 2012)

There are 2 different answers here.

It's code required.

If the site conditions mean there is no frost heave, a building will do fine with just a shallow concrete footer. 

Wind and seismic considerations are a different question.


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## Rio (Oct 13, 2009)

Here's a piece of architecture/construction trivia.............. Frank Lloyd Wright is widely credited as designing and building the first slab on grade houses and did so in the northern tier of the United States.


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## Ken360 (Sep 7, 2019)

Rio said:


> Here's a piece of architecture/construction trivia.............. Frank Lloyd Wright is widely credited as designing and building the first slab on grade houses and did so in the northern tier of the United States.


Frank Lloyd Wright HATED basements.


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## DiegoGo (7 mo ago)

TheWagonmaster said:


> I live in the northern US, and I've noticed that some buildings up here don't have a basement. My employer's building, for instance, has no basement. Many cabins are also basement-less, and of course manufactured homes also "sit" on top of the soil.
> 
> I was under the impression that all buildings needed to be built below the frost line for structural stability. What am I missing here? Are these people taking a gamble that their buildings will deteriorate more quickly?


By the code book. Yes you will require it to be under the frost line every time. Depending on where you live it can be different. PNW it's going to be 18"


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## sunkist (Apr 27, 2012)

We worry more about the BFE than any frost line BFE= Base Flood Elevation


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