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About This Calculator
Calculate cylindrical Sonotube cardboard tube concrete volume, required 60lb and 80lb ready-mix bags, and frost line depth requirements for deck pier foundations.
Frequently Asked Questions
How deep must deck Sonotubes be placed?
Deck footings must extend at least 6 to 12 inches below the local frost line (typically 36 to 48 inches in northern US states) to prevent frost heaving from lifting and destroying the deck frame during winter freeze-thaw cycles.
How many 80-pound concrete bags are in one cubic yard?
One cubic yard (27 cubic feet) requires exactly 45 bags of 80-pound pre-mixed concrete (or 60 bags of 60-pound concrete).
Why should 12-inch Sonotubes be used instead of 8-inch for deck posts?
An 8-inch tube leaves almost zero margin for error when placing post anchor brackets. A 12-inch tube allows easy alignment of 6x6 posts and distributes structural load over more than twice the soil bearing area (113 sq in vs 50 sq in).
What is the benefit of a flared bell footing base (Bigfoot)?
A flared bell base dramatically increases soil contact area to resist frost uplift, prevents settling in soft soils, and eliminates the need to pour separate concrete footings before installing the tube.