Oops, I didn't catch that (I'm used to an active zone of 10 ft or so here in
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
From: John P. Riley [mailto:jpriley485(--nospam--at)peoplepc.com]
Sent: Wednesday, April 04, 2001 9:55 AM
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
My first inclination is to overexcavate and backfill.
John P. Riley, PE, SE
20 Oakwood Drive, Blue Grass, Iowa 52726
Tel & Fax: 319-381-3949