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# footing size chart

#1
07-13-15, 11:09 AM
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Join Date: Jul 2015
Location: United States
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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?

#2
07-13-15, 01:31 PM
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Join Date: Feb 2006
Location: USA
Posts: 6,605
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.

#3
07-13-15, 01:55 PM
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Join Date: Jul 2015
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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.

#4
07-14-15, 11:26 AM
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Join Date: Sep 2009
Location: Louisville KY
Posts: 578
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.

#5
07-14-15, 12:22 PM
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Join Date: Mar 2005
Location: USA
Posts: 6,130
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

#6
07-14-15, 03:15 PM
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Join Date: Jul 2015
Location: United States
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Msradell. Yes. I'll try to attach it.

#7
07-14-15, 03:29 PM
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Join Date: Jul 2015
Location: United States
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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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