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I am looking to have a 20'x24' unheated detached garage built on the slope of my property. The back of the garage would have about 5' high foundation above soil, with blocks stepped along the sides as needed, plus the parking slab. Then a typical wood garage framed on top. I live in MN where the frost line is typically down to 42". Both of the companies I have gotten the most comprehensive bids from do not propose to do a frost footing, but only use strip footings, concrete blocks and bond beam. I asked about whether a frost footing should be done and they said that this foundation would basically act as a floating foundation and move together. A frost footing could be done for another 4k they replied after asking. Other concrete professionals (who focused on flatwork only so didn't bid) suggested that I should not allow anyone to not do a frost footing. Everything I can find online only speaks to monolithic slabs being floating. Can someone who does this type of block work in cold climates help with this quandry of whether a frost footing is needed structurally?
 

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I'm not a pro, and don't know what a strip footing is. I do know, however, that SOMETHING has to take the weight of your building, including snow loads, and transfer that to the soil. You can figure your house weight (approx) by using 20 lbs/sf on the roof, plus snow load/sf. Convert that to linear feet, and get a rough idea of your load on your walls. Your soil is something like (I am guessing) capable of carrying 2000 psf, but that depends greatly on your particular spot. Make sure you have a footer wide enough to match what the soil will bear; it may be 8", it may be 20". I'd suggest you see an engineer in the area.
 

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I am looking to have a 20'x24' unheated detached garage built on the slope of my property. The back of the garage would have about 5' high foundation above soil, with blocks stepped along the sides as needed, plus the parking slab. Then a typical wood garage framed on top. I live in MN where the frost line is typically down to 42". Both of the companies I have gotten the most comprehensive bids from do not propose to do a frost footing, but only use strip footings, concrete blocks and bond beam. I asked about whether a frost footing should be done and they said that this foundation would basically act as a floating foundation and move together. A frost footing could be done for another 4k they replied after asking. Other concrete professionals (who focused on flatwork only so didn't bid) suggested that I should not allow anyone to not do a frost footing. Everything I can find online only speaks to monolithic slabs being floating. Can someone who does this type of block work in cold climates help with this quandry of whether a frost footing is needed structurally?
Call your building department and ask them.
 

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I talked to the building dept. Although the structural engineer seemed to think it would be fine pending soil conditions, he wanted to make sure the specific inspector for our area would accept it. The inspectors first response was "no way" and "I have seen to many of these blow out after just short time":furious:. "Get bids for the project to include frost footings." I talked again to my concrete guy who was certain it was fine. He talked to the inspector the next day, explained the plan and the inspector told me the design will basically have the same effect as frost footings and that I could save my money instead of putting to frost footings.:yes: He also mentioned that companies make a big difference and he is not comfortable with a blanket rule to allow this practice. Talk about back and forth!:eek:
 
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