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Concrete pier hack question

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#1 jambi99

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Posted 13 July 2020 - 03:17 PM

Hi there,

 

would it be acceptable to raise the ground level around the pier to increase the pier depth? I was thinking raising the ground of about 6-8 inches on a 4x4 feet surface to reach the 6 feet recommended frost line depth.

 

Thanks



#2 Jim Waters

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Posted 13 July 2020 - 04:32 PM

Unless you pack it down real hard, No.



#3 Simcal

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Posted 13 July 2020 - 04:39 PM

Did a google and Ottawa frost line is 1.8m or 5.9 feet. But that is a building code generalization not taking into account the type of ground, ground water in the site, drainage, exposure to sun etc.   If you're saying you're at 5.4' feet depth, then I wouldn't worry about adding 6".  

 

Even if the pier does move, you can always re-align the mount every year.  It's likely only going to budge during the initial freeze-up in December, and spring thaw in March/April. 


Edited by Simcal, 13 July 2020 - 04:40 PM.


#4 bouvier_1

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Posted 13 July 2020 - 04:50 PM

Lay some 2" rigid insulation down and cover with 6" of dirt



#5 macdonjh

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Posted 13 July 2020 - 06:11 PM

I don't think that will work to prevent frost heave.  The soil freezes not only from the top down but would also freeze laterally from the edges of your raised areas.

 

Curious: why is not digging to the frost line feasible?



#6 piaras

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Posted 13 July 2020 - 07:06 PM

Foam will work if it covers several feet in radius. We would place a few bales of hay/straw around the well to stop freezing. If you are placing a deck around the pier, use the deck to hold the foam down. I likely would not worry about it. If you are in a windswept area where the snow cover gets blown away and the pier is exposed at ground level then freezing will have better chance of getting to depth. Our water line from the well was at 7 feet and late in the winter, one harsh week of intense cold and no snow cover, it froze. The new line is heat taped.
In my area 4 feet is minimal and my pier is just there. With a deck and Skyshedpod on top, I realign in the spring and over the years it has been only a slight movement.

Pierre



#7 t-ara-fan

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Posted 13 July 2020 - 10:33 PM

 

Curious: why is not digging to the frost line feasible?

Indeed. Why not dig another 6"? Or a foot just to be sure.  If it is because you hit bedrock that is a good thing.



#8 jambi99

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Posted 14 July 2020 - 07:27 PM

The auger I rented does not go deeper than 5 feet. Doing the remaining 1 foot is rather challenging considering how narrow the hole is. But I agree, I will try to reach the required (by code) 6 feet by digging deeper. Thanks for your feedback.



#9 piaras

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Posted 15 July 2020 - 09:10 AM

Would seem that the rental place would supply the extension to reach frost line automatically as it is a requirement for the building code.

Pierre


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#10 macdonjh

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Posted 15 July 2020 - 09:21 AM

Would seem that the rental place would supply the extension to reach frost line automatically as it is a requirement for the building code.

Pierre

+1



#11 jambi99

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Posted 15 July 2020 - 11:50 AM

Would seem that the rental place would supply the extension to reach frost line automatically as it is a requirement for the building code.

Pierre

Yes, the extension was included already. Still limited to 5 feet. 



#12 macdonjh

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Posted 15 July 2020 - 11:59 AM

Yes, the extension was included already. Still limited to 5 feet. 

Hmm.  When I rented an auger for my pier, I rented two extensions for a total of nine feet.  I wonder if you could rent another extension?

 

I ended up using all three auger sections, but only going down a bit more than six feet.  I hit a second layer of sand and there wasn't any point in going deeper.



#13 jambi99

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Posted 16 July 2020 - 09:15 AM

Hmm.  When I rented an auger for my pier, I rented two extensions for a total of nine feet.  I wonder if you could rent another extension?

 

I ended up using all three auger sections, but only going down a bit more than six feet.  I hit a second layer of sand and there wasn't any point in going deeper.

My understanding is that the maximum total bit length was 5 feet so I never asked for anything longer than that. However, you might be right. In any cases, I dug the hole already and I don't want to have to rent another auger. I will have to dig the reaming 6 inches by hand and will 2 inch foam board as suggested above to mitigate the frost. Thanks.


Edited by jambi99, 16 July 2020 - 09:16 AM.


#14 jambi99

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Posted 21 July 2020 - 08:57 AM

Just an update. I was able to reach a total depth of 6' 4" . Pretty happy with that. Thanks for your help.


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