footing size chart

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Old 07-13-15, 11:09 AM
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footing size chart

This San Diego County footing size chart is confusing to me. Can someone tell me what they mean?
Name:  footing size.jpg
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Old 07-13-15, 01:31 PM
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Table

The left column is post spacing expressed in feet.

The top row of numbers in bold print is joist span in feet.

The body of the chart is the footing size in inches per side.
 
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Old 07-13-15, 01:55 PM
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The body of the chart is the footing size in inches per side.

So...... If I come up with the number 24 on the chart that means the footing will have to be two foot by two foot on top? 576 square inches? Seems big.
 
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Old 07-14-15, 11:26 AM
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Actually, if I look at the various points on the chart the numbers seem about right. Is there another section of the chart that shows how deep the footings have to be? That's just as critical as the surface area.
 
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Old 07-14-15, 12:22 PM
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Charts like that almost always over estimate the sizes. That is because amateurs do the determination of the sizes and there is question about the bearing capacity, so a lower soil capacity is assumed.

There should have been information on the footing thickness, especially with both top and bottom #4 reinforcing steel.

Just an example of prescriptive design to keep thing simple.

Dick
 
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Old 07-14-15, 03:15 PM
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Msradell. Yes. I'll try to attach it.Name:  footing depth.jpg
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Old 07-14-15, 03:29 PM
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Since I'm on a roll here. I'd like to ask another question about this.
Am I allowed to convert that 576 sq in. to a round area so I can use a Sonotube form? Actually since my post spacing is about 6 1/2 feet with a 10 foot joist span, I changed the 24 to 23 and came up with 529 sq. in. That would be a 26 in. Sonotube form. Look right?
 
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