frost depth at garage

[DoubleStud]

So the frost depth at this project is 4 ft. One side of garage wall is basically retaining soil. My question is, where is the frost depth inside the garage when it is against the soil? Do we measure the frost depth from the garage slab since it is unheated space? Or do we measure it from the finish grade? The wall will retain about 4-5 ft of soil at some spot. I added green line where the highest is going to be, But probably not sloping to the house. I messed up my sketch.

 

[JStructsteel]

Its 4'-0" down from the front, so you could step up the footing at the side if you wanted to

 

[DoubleStud]

JStructsteel, just have to make sure garage is insulated? It is ok if not heated?

 

[Enable]

The interior of the garage will be close enough to the ambient temperature that you should take your datum as the garage slab elevation all the way around. If you want to take advantage of the soil on the exterior side to reduce footing depth, you can place 4" of XPS insulation underneath the SOG adjacent to the wall and extend it 4' inwards. But by the time you do that and add costs for a stepped footing you probably won't have saved much.

 

[HTURKAK]

- For perimeter column ftgs , measure from the exterior finished grade ,

- For interior , from the finished grade but the temp. in the garage will be less than exterior ambient temp. due to closed and attached to the heated bldg.

- I will suggest you to use XPS insulation and frost free material ..

- Refer to ASCE 32-01 Design and Construction of Frost-Protected Shallow Foundations..

Not to know is bad;
not to wish to know is worse.

NIGERIAN PROVERB

 

[Canuck65]

You cannot step the footing up along the side.
The garage is unheated, therefore the datum is measured from top of the interior garage slab floor.
The only way to reduce the footing depth would be via the use of properly designed insulation under the garage slab.