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Frost Protected Building Addition

Frost Protected Building Addition

Frost Protected Building Addition

(OP)
I was out for foundation checks on a building addition project and found out the the original building was simply a SOG over 6-12" of granular material. We have a design frost depth of about 42" here so the addition has been designed to bear below the frost elevation. I am a little concerned about the tie-in location. Structurally speaking, the addition is fully self-supporting, but exterior roof/wall finishes will be tied together. The existing building is fully heated and is a retail building, so the slab will always be kept warm, but I don't think that heat will push deep enough to prevent frost from developing and moving the existing building.

Are my concerns well founded or am I overthinking this one? Is there a good way to seal the building up, while allowing for relative movement between the two buildings?

RE: Frost Protected Building Addition

There might be, but if the existing building has performed well, why not use a slab on grade to support the addition? At least it would be consistent.

BA

RE: Frost Protected Building Addition

how old is the original building and are there any signs of damage from frost heave? Cold is only 1 ingredient required for frost heave, so maybe its not an issue for your particular project. How is your 42" deep foundation going to tie into the slab on grade?

If you're really concerned about it and you feel something has to be done you could have them insulate the existing slab on the outside to provide the 42" frost protection.

RE: Frost Protected Building Addition

What is the soil type under the slab? It may well be non-frost susceptible such as clean sand. That cook book number of "frost depth" may well be OK in general, but different degrees of frost susceptibility as well as water present make such an assumption meaningless in many cases. A Badger land person in LaCrosse can tell you freezing can well go down 8 feet due to minimal moisture in sand there, yet no heaving occurs. Non-frost susceptible explains it.

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