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Calculate concrete volume, bags needed, and rebar requirements for round, square, or rectangular columns. Perfect for estimating Sonotube and cylindrical column pours.
D=diameter (in), S=side (in), L=length (in), W=width (in), H=height (ft), V=volume (cu yd)
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A concrete column is a vertical structural element designed to support compressive loads from beams, slabs, or roofs above. Columns transfer these loads safely to the foundation.
Concrete columns come in three main shapes:
Where D is the diameter in inches and H is the height in feet.
Where S is the side length in inches and H is the height in feet.
Where L is length, W is width (both in inches), and H is height in feet.
Concrete volume per linear foot for common Sonotube diameters:
| Diameter | Cu Yd per Foot | 8 ft Column | 10 ft Column |
|---|---|---|---|
| 6" | 0.0073 cu yd | 0.058 cu yd | 0.073 cu yd |
| 8" | 0.0129 cu yd | 0.103 cu yd | 0.129 cu yd |
| 10" | 0.0202 cu yd | 0.162 cu yd | 0.202 cu yd |
| 12" | 0.0291 cu yd | 0.233 cu yd | 0.291 cu yd |
| 14" | 0.0396 cu yd | 0.317 cu yd | 0.396 cu yd |
| 16" | 0.0517 cu yd | 0.414 cu yd | 0.517 cu yd |
| 18" | 0.0654 cu yd | 0.523 cu yd | 0.654 cu yd |
| 24" | 0.1164 cu yd | 0.931 cu yd | 1.164 cu yd |
Add 10% for waste and overfill. Sonotube is a registered trademark of SFS intec, Inc.
Vertical rebar reinforces concrete columns against bending and tension forces. Common configurations:
Minimum reinforcement for 8-12" diameter columns. Four vertical bars, 1/2" diameter (#4 rebar).
Medium-duty columns 12-16" diameter. Six vertical bars, 5/8" diameter (#5 rebar).
Heavy-duty columns 16-24" diameter. Eight vertical bars, 5/8" diameter (#5 rebar).
Horizontal ties hold vertical rebar in position. Standard spacing: 12 inches on center (OC) for columns under 12 ft tall. For taller columns, use 8-10" spacing.
Maintain 1.5-2 inches of concrete cover around all rebar. This protects steel from corrosion and fire. Use plastic spacers or chairs to position the cage.
Always verify rebar requirements with local building codes and engineer specifications. Structural columns require professional engineering.
Sonotubes (cardboard tubes) are ideal for round columns - they're inexpensive, lightweight, easy to install, and can be left in place or peeled off. Use wood forms for square/rectangular columns or when you need reusable forms for multiple pours.
The cage should be 3-4 inches smaller in diameter than the column to allow proper concrete cover. For a 12" column, build an 8-9" diameter cage. Use plastic spacers to center the cage and maintain 1.5-2" cover all around.
For Sonotubes, pour up to 10-12 feet in one continuous pour. Taller columns risk form blowout from concrete pressure. For heights over 12 feet, use stronger forms, external bracing, or pour in lifts.
Set the tube plumb using a level, then brace with 2x4s staked to the ground in 3-4 directions. Check plumb again before pouring. For tall columns, add mid-height bracing to prevent bowing during the pour.
A 12" diameter × 8 ft tall Sonotube needs approximately 0.233 cubic yards or 10-11 bags of 80lb concrete mix. Always buy 10-15% extra for waste, spillage, and form overfill.
Wait at least 24-48 hours before removing Sonotube forms, longer in cold weather. Wood forms can typically be removed after 24 hours. Don't load the column until it reaches design strength (usually 28 days).
Yes, use a concrete vibrator or tap the outside of the form with a rubber mallet while pouring. This eliminates air pockets and ensures proper consolidation, especially around rebar. Don't over-vibrate or you'll cause segregation.
Round Sonotube columns can be left with a smooth finish, textured by peeling the form partially, or wrapped with decorative material. Square columns can be finished with stone veneer, stucco, wood wraps, or architectural concrete finishes.
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