Posted 1/21/2025 11:38 (#11066504 - in reply to #11066149) Subject: RE: Concrete under sliding doors, best way to form
EC IL
We had one 9' barn door approach that looked like the others, but never heaved in the winter. We had to tear it out to modify something else and found out why it never moved.
They didn't form the whole approach 4' deep (frost line here) but instead had dug 2 postholes about 4.5' deep and filled them with concrete as they poured the approach. That technique must have created just enough heat transfer to keep the subgrade under the rest of the approach from freezing. So that's how we started doing all our other under-door concrete jobs at home. Just form the top as you feel is needed, but put a deep post hole every 3-4' along the length. Less concrete than forming the whole thing below the frost line.
Concrete under sliding doors, best way to form
