# Building On A Lot With Bad Soil?



## rstarre (Dec 19, 2008)

I have a client who has a vacant lot that is in a 100 year flood zone and has 10 ft deep of bad ground. The village will allow her to build as long as she uses piers/pylons. My question is how many feet do you have to put a pier under the footing?


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## dayexco (Mar 4, 2006)

to whatever depth your soils engineer and architect tell you to?


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## griz (Nov 26, 2009)

This will involve more plans, engineering & excavation than you can imagine. 
The fact you are asking this question is why you should have nothing to do with this project.


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## Nac (Apr 16, 2006)

The lot need borings done in several locations. Then A Geo-tec can come up with the info you need based and the load requiments by the structrual eng. and the type of piles speced. Where is the job located?


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## Driftwood (Feb 15, 2004)

*Chance helical anchors*

Here in the bay area we often drill 18" peir holes 11 ft into rock. For expansive soils You can't beat chance helical anchors. I have 5 under one side of My home. I jacked up one side of a slab on grade foundation 3 1/2" two struct. engineers couldn't believe I was able to do this.


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## tcleve4911 (Mar 26, 2006)

rstarre said:


> i have a client who has a vacant lot that is in a 100 year flood zone and has 10 ft deep of bad ground. The village will allow her to build as long as she uses piers/pylons. My question is how many feet do you have to put a pier under the footing?


where is the project located????????


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## PipeGuy (Oct 8, 2004)

rstarre said:


> ...how many feet do you have to put a pier under the footing?


What's the budget for piers?


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## ConstSvcs (Nov 22, 2007)

This how we handle it (us & what we do):

http://www.youtube.com/watch?v=5StJtqtez8g


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## loneframer (Feb 13, 2009)

Having seen a few thousand homes built on pilings, I can tell you, the length of pole required can vary from lot to lot.

Standard procedure here is to drive several test poles on the lot. An engineer will be on site to do a "blow count". Which means a specific weight is dropped from a specific height and once the pole fetches up, the calculations come into play as to how much weight the pole will bear. At that point, the proper length poles are ordered for that specific job site.

Most of the homes I built had somewhere in the area of 40 poles under it. Some had many more. I've seen 30' poles and I've seen 65' poles within few blocks of each other. A few miles away, on the same island, the soil was stable enough that it didn't require pilings.


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## tcleve4911 (Mar 26, 2006)

Nice video
That's what I was trying to describe in my Deck Progress thread.

....and this is what you do?

Have you heard of Techno Posts? same idea ...helical posts.

Thanks for showing that.

I may hyjack the video to show the process but I'll get out of here so I don't hyjack the thread.:biggrin:


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## greg24k (May 19, 2007)

Engineer will come up with a design criteria for the pad. You will have to remove the soil to required depth, and fill it with layers of stone so the sub-grade is compacted to density in excess of 95% of the maximum dry density which must meet ASTM D ## (not sure what number,haven't done this in a while) engineer will have that info. When you cut the soil down and there is water present, you will have to over-excavate 6-12" and put the stone down and compact to 5,600 LB PF to provide de-watering media.

It's a little more of a pain in the A$$ then building on regular lot, but it's doable :thumbsup:

Good luck


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## Covenant (Jun 6, 2009)

Where is the jobsite?


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## mc handyman (May 17, 2009)

tree foot fiddy inches!:nerd: Its standard. :thumbup:


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