How do I design a foundation that will be frozen and thawed yearly?

by Sherwood Botsford   Last Updated August 01, 2020 14:21 PM

I currently have a 12x12 insulated shed on slab on grade. I use it to store seedlings during the planting season. I pre-chill the room by opening it in winter and using a box fan to circulate air between inside and outside. In addition I have 3/4 full barrels of water.

This works. This year I had ice in the barrels until mid July.

I need to build a larger room.

My concern is that I am deliberately allow the foundation to freeze -- indeed, the whole point is to get the foundation to freeze. All the conventional wisdom is that buildings need to be supported on something that stays put, and that freeze thaw cycles don't guarantee this.

This hasn't been a problem so far, but perhaps I'm just lucky. The building footprint is small, so if the slab shifts as a whole, I may be getting away with it.

Yes: I know that conventionally I would put in a massive chiller and insulate the floor too. I only need cooling for 6 weeks a year. Conventional actions seem like overkill.

My current thinking is that I need to ensure that the foundation volume is well drained. Shifts are caused by the expansion of water into ice. If the water content is minimal, then the foundation will stay put. I'm leaning toward a rubble or rock filled trench for the foundation,E.g. Dig X feet, line trench with infiltration cloth, lay weeping tile with a sump, fill with rock, top with road crush, and set my foundation.

I thought of going the pole barn route:

Auger deep holes Y feet deep, and use poles as the support structure, and NOT putting down a concrete floor inside. The poles would need to be set with a slip layer (several layers of 12 mil poly?) on the part of the pole that was in the freeze thaw zone. Walls themselves would need to be designed with a potential sacrificial layer for the bottom to accommodate rising and falling ground levels. (Some form of compressible insulation?)

Can someone point me to resources for designing foundations that are supposed to freeze and thaw?



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