Shallow Grade Beams and Frost

[wadavis]

I am working on a few designs in Alberta that include shallow grade beams (12" steel beam 2" above grade, 10" preserved wood beam 2" below grade, 12" concrete). With the close pile spacing and and void forms, I'm not to concerned about the grade beams and structures themselves.
It is the frost penetration extending under the shop's slab-on-grade and causing heaving that I'm curious about.

Is this an issue?

Or does the clean fill under the slab, building heat and adequate site drainage prevent heaving sufficiently?

Regards,
Wadavis

 

[shobroco]

Insulate the perimeter or you will have problems. You can insulate horizontally or vertically, just remember that the frost has to travel the same distance regardless of direction. 2" of R5/inch rigid foam will replace about 2' of soil cover.

 

[oldestguy]

Remember also how frost travels. As below freezing temps contact moisture,the moisture gives up heat, slowing the progress of freezing. So, where you have sandy soil, it can travel a lot farther than some of the so-called- "frost penetration" depths.

Thus, it goes deep (and horizontal) in low moisture soils, as sands. But does not go so far in clays that have high moisture content. Luckily sands are low frost potential for heaving.

Thus, a shallow depth insulation zone may not do much for you, since it follows the easiest path, so to speak.

 

[wadavis]

Thanks for the input,
Will be using an insulated dog leg to get the most insulation out of the least excavation.