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Re: Foundation on Expansive Clay

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Unfortunately, it appears that these expansive clays extend to China.

1.  What would a couple feet of undercut and backfill gain me?

2.  How likely am I to get differential movement in excess of 1/2" in a
yard foundation 7ft x 8ft?

Fountain

----------
> From: Bill Polhemus <bill(--nospam--at)polhemus.cc>
> To: seaint(--nospam--at)seaint.org
> Subject: RE: Foundation on Expansive Clay
> Date: Wednesday, April 04, 2001 11:02 AM
> 
> Oops, I didn't catch that (I'm used to an active zone of 10 ft or so here
in
> Southeast Texas).
> 
> You're right, John. If it's only a 6 inch active zone, excavating it out
is
> the best alternative. In fact, I'd recommend doing that up to about 5 or
6
> feet or so. After that, it's worth looking at a cost comparison.
> 
> William L. Polhemus, Jr., P.E.
> Polhemus Engineering Company
> Katy, Texas
> Phone 281-492-2251
> Fax 281-492-8203
> 
> 
> -----Original Message-----
> From: John P. Riley [mailto:jpriley485(--nospam--at)peoplepc.com]
> Sent: Wednesday, April 04, 2001 9:55 AM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Foundation on Expansive Clay
> 
> 
> "My thinking is to turn down the outside edge of the footing an
additional 6
> inches.  If this clay is expansive, it shouldn't be given to capillary
> action, and will provide a seal, preventing the soil beneath the
foundation
> from seeing the varying moisture content."
> 
> Is the expansive clay layer only 6" thick?  If this "turn-down" method is
> effective in protecting the soil within the 6" zone, what about the soil
> beneath IT?
> 
> My first inclination is to overexcavate and backfill.
> __________________
> John P. Riley, PE, SE
> Riley Engineering
> 20 Oakwood Drive, Blue Grass, Iowa 52726
> Tel & Fax:  319-381-3949
> jpriley485(--nospam--at)peoplepc.com