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RE: Foundation on Expansive Clay

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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)]
Sent: Wednesday, April 04, 2001 9:55 AM
To: seaint(--nospam--at)
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