Question 1

How much concrete does a Sonotube hold?

Accepted Answer

Use the cylinder formula: π times the radius squared times the height. A 12-inch tube 4 feet deep holds π × 0.5² × 4 = 3.14 cubic feet, or 0.12 cubic yards — about six 80-lb bags.

Question 2

How many bags of concrete per Sonotube?

Accepted Answer

A 12-inch tube 4 feet deep takes about six 80-lb bags. An 8-inch tube of the same depth takes three. Multiply by your tube count and add 10% — running short mid-pour leaves a cold joint in a structural element.

Question 3

What size Sonotube do I need for a deck?

Accepted Answer

Ten or twelve inches covers most residential deck footings, but the correct size depends on tributary area, soil bearing capacity, and load. DCA 6 has the sizing tables, and this is one place where guessing is a genuinely bad idea.

Question 4

How deep should a Sonotube footing be?

Accepted Answer

Below the local frost line, which ranges from none in the far south to 48 inches or more in northern states. A footing above frost depth will lift each winter and take the structure with it.

Question 5

Do I need a footing under a Sonotube?

Accepted Answer

Usually yes — a wider pad at the base spreads the load into the soil. Many jurisdictions require a bell or a separate poured footing, and some accept a manufactured plastic footing form attached to the tube.

Question 6

Should I remove the cardboard tube after pouring?

Accepted Answer

Strip the exposed portion above grade after the concrete sets, since cardboard left on absorbs water and looks poor. Below grade it can stay; it decomposes harmlessly and removing it risks disturbing the backfill.

Question 7

Do Sonotube footings need rebar?

Accepted Answer

Most codes require vertical rebar in piers carrying structural load, typically two to four bars with ties, plus an anchor bolt or post base cast into the top. Check your local requirement rather than assuming.

Question 8

Can I pour Sonotubes in cold weather?

Accepted Answer

Below 40°F you need cold-weather measures under ACI 306 — heated water, accelerators, and insulated blankets. A narrow column loses heat fast because of its high surface-to-volume ratio, so it is more vulnerable than a slab.

Sonotube Calculator

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