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Re: Floating Foundation ?
From: info@builderswebsource.com
Category: Foundations and Basements
Remote Name: 63.198.181.43
Date: 16 Aug 2001
Time: 09:06 PM
Comments
As we indicated in our previous messages, we strongly advise that you retain
a geotechnical company to survey the property and make foundation
recommendations based on the actual soil conditions. Planning for proper
drainage is absolutely essential to ensuring good foundation performance over
the life of the structure. If you do not have a specific drainage plan with
proper grading away from the foundation, you're asking for trouble! Don't let
anyone convince you otherwise.
To provide additional insight into floating slab foundations, attached is an
excerpt from the website of Geotech Engineering (http://www.geotecheng.com),
which specializes in geotechnical studies and foundations on expansive clay
soils in Texas:
Floating Super-Structural Slab Foundation (Conventionally-Reinforced
or Post-Tensioned Slab)
The risk on this type of foundation system can be reduced
significantly if it is built and maintained with positive drainage and
vegetation control. No piers are used in this type of foundation. Many
of the lightly-loaded structures in the state of Texas are built on this
type of foundation and are performing satisfactorily. In the areas where
trees have been removed prior to construction and where expansive clays
exists, these foundations must be significantly stiffened to minimize
the potential differential movements as a result of subsoil heave due to
tree removal. The beauty of this foundation system is that as long as
the grade beams penetrate a minimum of six-inches into the competent
natural soils or properly compacted structural fill, no compaction of
subgrade soils are required. The subgrade soils should; however, be firm
enough to support the floor slab loads during construction. The
structural engineer should design the floor slabs such that they can
span in between the grade beams. The subsoils within which the grade
beams are placed must have a minimum shear strength of 1000 psf and a
minimum degree of compaction of 95 percent standard proctor density
(ASTM D 698-91) at a moisture content within ±2% optimum moisture
content.
Floating Slab Foundation (Conventionally-Reinforced or
Post-Tensioned Slab)
The risk on this type of foundation can be reduced significantly if
it is built and maintained with positive drainage and vegetation
control. No piers are used in this type of foundation. Many of the
lightly-loaded structures in the state of Texas are built on this type
of foundation and are performing satisfactorily. In the area where trees
have been removed prior to construction and where expansive clays
exists, these foundations must be significantly stiffened to minimize
the potential differential movements as a result of subsoil heave due to
tree removal. However, foundation tilt can still occur even if the
foundation system is designed rigid. |
We hope this helps!
Builders Websource
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