Frost penetrating drainage gravel too deeply?
I just had a contractor warn me against installing drainage gravel the full height of the foundation wall (below grade).
He told me that here in the mountains of Virginia (Climate zone 4A, mixed humid), he had a client that once had their water line freeze solid next to the foundation, at a 5 foot depth – when our maximum frost depth is normally only 2 feet.
He figured out that the frost had penetrated extremely deep next to the foundation because someone had put drainage gravel the full depth of the backfill. And the open gravel allowed the cold to penetrate much deeper than usual.
Has anyone here heard of that happening before?
I was planning on installing drainage gravel most of the height below grade, with the exception of an underground gutter draining water away from the foundation below a 2″ thick layer of finely crushed stone.
However, the top of my footings are only 28″ below grade, and my drainage gravel extends to the bottom of the footings on the one side with the foundation drain. We also have dimple membrane as a water barrier on the poured concrete foundation wall for our crawl space, and a 2 foot wide eave overhang above.
He recommended backfilling with soil for the top 12″, to prevent frost from penetrating too deeply. I’m a stickler for good moisture control, which is why I had wanted gravel backfill for nearly the full depth. But now I’m concerned about the cold.
Any thoughts or suggestions about this? Thanks.
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