# Digging Footings 42" Deep (Hydro)



## hdavis (Feb 14, 2012)

Californiadecks said:


> So the part of the house footing that's in the ground doesn't touch the sides of the dirt?


Not when it's poured.


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## Calidecks (Nov 19, 2011)

hdavis said:


> Not when it's poured.


When it's back filled?


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## Calidecks (Nov 19, 2011)

Here's an example of footings I did on an addition. Those footings are 18" deep. Sucks to be you guys sometimes, with that crazy thing you all call frost heave!


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## Tinstaafl (Jan 6, 2008)

brhokel606 said:


> Frost starts at the top and works it's way down, so wouldn't that lock the footing in?


It doesn't work quite like that, especially if you take "adfreezing" into account. Pretty good description here:

http://www.concretenetwork.com/conc...ow_footings/frost_actions_and_foundations.htm

IMO, sonotube to the frost line and a nice wad kissing the dirt under that (extra credit for belling it) is about as good as you can do practically.


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## Calidecks (Nov 19, 2011)

That would fail inspection here. The dirt you pull out of the ground to put the sonotube in and then pack back around the footing would need compacted.


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## EricBrancard (Jun 8, 2012)

Californiadecks said:


> That would fail inspection here. The dirt you pull out of the ground to put the sonotube in and then pack back around the footing would need compacted.


You just use a tamper bar when back filling.


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## Calidecks (Nov 19, 2011)

Most all my plans say Concrete in undisturbed soil.


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## hdavis (Feb 14, 2012)

Californiadecks said:


> When it's back filled?


Usually you just leave the tube in place. Depending on the forms, you may leave them in place, too.


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## slowsol (Aug 27, 2005)

Californiadecks said:


> When it's back filled?



We backfill with stone. 


Sent from my iPhone using Tapatalk


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## hdavis (Feb 14, 2012)

Californiadecks said:


> Most all my plans say Concrete in undisturbed soil.


The way it's read round here is depth has to be 48" or to undisturbed soil, which ever is deeper. Same as doing a full basement footer / wall.


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## hdavis (Feb 14, 2012)

Tinstaafl said:


> It doesn't work quite like that, especially if you take "adfreezing" into account. Pretty good description here:
> 
> http://www.concretenetwork.com/conc...ow_footings/frost_actions_and_foundations.htm
> 
> IMO, sonotube to the frost line and a nice wad kissing the dirt under that (extra credit for belling it) is about as good as you can do practically.


Agreed. Working off of prints, they don't call for belling that I've seen, so I don't bell. No prints, I will bell.


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## EricBrancard (Jun 8, 2012)

Californiadecks said:


> Most all my plans say Concrete in undisturbed soil.


It's supposed to sit on undisturbed soil. The sides don't have to be.


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## hdavis (Feb 14, 2012)

EricBrancard said:


> It's supposed to sit on undisturbed soil. The sides don't have to be.


I'll grant a possibility that Cali could be different from the rest of the country.:laughing:


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## EricBrancard (Jun 8, 2012)

I'm dreading having to dig 3 footings tomorrow. Never again. Lapse in judgement.


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## Xtrememtnbiker (Jun 9, 2013)

Here, we dig an 18" hole and drop a 12"x12"x8" poured concrete pier block in the bottom, build the deck, call for one inspection at the end, pass, and back fill the holes.

Sounds like it sucks to build decks in the rest of the world. :laughing:

Well, except for the helical guys, that's how I'd want to do it.


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## Calidecks (Nov 19, 2011)

hdavis said:


> I'll grant a possibility that Cali could be different from the rest of the country.:laughing:


It's very different and not near as stringent when it comes to footings. It's because of the weather. I don't even need them for some decks.


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## Calidecks (Nov 19, 2011)

EricBrancard said:


> It's supposed to sit on undisturbed soil. The sides don't have to be.


Depends on what it is. If it's a slab on grade with an exterior footing you can't have just tamped soil on the inside where the slab is poured. In fact it needs to be 90% compact and there are times I have to get it tested. This is why if a footing side breaks we either bulkhead it off with drywall and back fill with sand or we do nothing and fill it with concrete. If we back fill with soil it needs to 90%. That's not practical to do here with all the clay.


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## Calidecks (Nov 19, 2011)

This one's better


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## Calidecks (Nov 19, 2011)

Into native soil not on top of native soil


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## Calidecks (Nov 19, 2011)

When you're in a high seismic zone the sides of the earth count for lateral movement.


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## PCI (Jun 8, 2012)

For pier footing, in MN, the footing is the part below the frost line. If code requires a 27" footing, it is this footing below the frost line. 

You can drop in a 6" sono a 8" sono or a 20" sono. 

The footing is below. 

The footings should be "belled" to anchor it.


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