Hi Ian,

If you have that much unknown clay depth, there may not be
much one can do to make it stabile outside of increasing the
concrete pier width as much as possible.  I do think it might
be helpful to drive some iron/steel rebars or whatever, into the
clay to whatever depth, and concrete pouring a portion of the
tops of the iron/steel into the pier to help improve the stability.
Normally....using steel (horizontal re-inforcement) isn't
recommended of course; but the vertical iron/steel might help
stabilize it abit more.  The clay might be more resistant to a
"test" driven rebar than known; so the feasibity, depth/length
might be gauged from that.

I envy your quiet location!  Good deal on the house extension!

Take care, Meredith

Ian Smith wrote:

> Many thanks to all who responded to my qs about concrete piers -
> Dewayne, Steve, Meredith & John.  Much appreciated.  I'm building a
> house extension in the next few months and will have some latitude in
> installing a pier.  The soil is clay like and the bedrock is a long way
> down.  So I'll dig as deep as I can afford and work by the many
> suggestions in the emails received.
>
> The good news is that my house is in the middle of a farm and the
> nearest (really quiet) road is over half a mile away.  So if I get the
> pier right, I should get some good results.  Of course, the extension
> will keep me busy for a while before I can turn to the seismo.
>
> Thanks
>
> Ian Smith


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