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More on Void Box No-No

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I've tried to send this through numerous times.

I'll try once again:

Let me give you all just one perspective on this topic. The following is
from a State of the Art report on geotechnical engineering issues for
residential and light commercial foundation design and construction,
approved last year by the Foundation Performance Association in Houston:

Void Boxes. About 38% of [geotechnical reports in the past five years]
specified the required void box size under the grade beams. Void boxes are
recommended by many geotechnical firms in Houston as a way of reducing
foundation movements. Expansive soils once swelled up can theoretically move
into a void space area (void box) without lifting the grade beams. The
discussion on whether or not void boxes should be used under grade beams on
residential foundations was conducted by the Foundation Performance
Association. It is generally believed that void boxes under grade beams
provide channels for water to flow underneath the foundation system.
Therefore, their use is discouraged. This discussion and idea was developed
in 1996.

As a result, again I say "In the past five years or so the use of Void Boxes
has been seen less and less in the Southwest." IMHO, those who still
recommend them aren't keeping up with the literature. Respectfully.



William L. Polhemus, Jr. P.E.
Polhemus Engineering Company
Katy, TX, USA
Phone (281) 492-2251
FAX (281) 492-8203
email bill(--nospam--at)polhemus.cc



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