midlf
Platinum Member
At work we had a problem with un-formed foundations on fences getting frost heaved. With formed concrete we had no such problems. The thought was that the un-formed concrete had too much "tooth" and the frost could grab it and push up even though hole was below frost line and the formed stuff had no place for the frost to grab. This did not happen everywhere but seemed to have some relationship to soil type and soil moisture. I wish I had more detailed info for you but my part of the correction project was just to budget for the cash needed.