Cob: Re: Foundation Strength Relative to Soil Type

[Myra Bonhage-Hale]

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Hi Kim, you can usually get your County Extension Agent or the Univ. of =
Arkansas Extension Service (you also have ATTRA there in Fayetteville) =
to give you a soil test - you can get the bags they supply at the county =
Extension Office and send them in - the analysis is usually free, unless =
you want to also know organic content.    The Extension Service also =
knows the prevailing soil type in your county.  Just take a sample at =
the proposed site of your house and send it in.  If the clay content is =
not enough, at least you will know what will grow there!!!!! - and they =
will also tell you what amendments need to be added for specific =
crops....Namaste.  Happy Holidays.  Myra
  ----- Original Message -----=20
  From: Kim West=20
  To: Cob List=20
  Sent: Friday, December 20, 2002 9:59 PM
  Subject: Cob: Foundation Strength Relative to Soil Type


  A while back I made a post relating the clay content of our soil here. =
A nice fella, I do not remember who it was, wrote to me that there is no =
way I can know the make-up of our soil without lab tests. Yesterday I =
found a book that I knew we had, yet did not know where it was. It is =
entitled "Soil Survey, Ouachita County Arkansas". After a bit of time =
studying the maps and information in the book, I now have a generic lab =
test result for our soil. Granted, it was not taken directly from this =
property, but it was a sample of this soil type.

  I found that our land is classified as Kirvin fine sandy loam. When =
this book was published, the classes of soil were standard country-wide. =
That was in 1973 so things may have changed somewhat, although the =
description would not change with the class name if indeed the class =
name has changed.

  =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
  What follows are some of the properties of Kirvin soil:

  Depth to seasonal high water table: 30-60 in.
  Depth from surface of typical profile:
      0-9 in......fine sandy loam........AASHO A-2 or A-4.........30-40% =
passing #200 sieve...shrink/swell low
      9-55 in....red clay, plastic.......AASHO =
A-7...................75-95% passing #200 sieve...shrink/swell moderate
      55-73.....silty clay loam..........AASHO A-4 or =
A-6..........60-75% passing #200 sieve...shrink/swell low

  Kirvin soil limitations relative to foundations of dwellings: Moderate =
if slopes are less than 15%; moderate bearing strength; moderate =
shrink/swell potential; severe if slope greater than 15%.

  As relates to septic systems: severe-slow percolation.

  =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

  Firstly, let me say that the depth to seasonal high water is no =
problem. We have lived here for nearly 13 years, through near-drought =
and through high precip years. Where I plan to build is atop a hill, the =
highest point on the property, and water has never been a problem, even =
during floods and/or high precip years.

  Secondly, The clay content given above pretty much agrees with the jar =
tests that I did. I had said that 6-12 inches down is pure red clay. The =
lab tests say that 9 inches down is 75-95% non-sand soil. This =
hypothetically could contain silt, but there are not three layers in my =
clay samples, only two. After the gentleman drew my attention to the =
need for a lab test, I did get a magnifying glass and do another =
examination using it. I found that under magnification the fine sand =
content that wasn't visible to my naked eye was indeed there. I owe him, =
whoever he was, a thank you for influencing me to back up and re-examine =
my samples. Had I not come across this soil survey I may have continued =
erroneously thinking the clay was pure. Thank you!

  Anyway, the reason I posted this is because of the previous =
discussions we have had on rubble trench foundations, and the fact that =
they have been around a while and work very well. I'm wondering if part =
of the success of those foundations was because they were set on stable, =
weight bearing soils. Above, it says the foundation limitations here are =
only moderate, meaning they can be overcome with good planning, so long =
as the slope is less than 15%. There is no problem here with that. Where =
I planned to build does indeed have a slope of less than 15%. My =
concerns, though, is the A-7 AASHO rating of the soil at 9-55 inches =
deep. A-1 is gravelly soil with a high bearing strength, and the scale =
goes down to A-7 which is clay with little strength if wet. If I built =
on top of the ground I would be working with an A-2 rating which is not =
bad, but once I dig down for the foundation I will be in A-7 soil which =
is the worst for weight bearing. I know I've been told "tamp, tamp, =
tamp...and good drainage is a must", and I know that is a very important =
part of building, but I am not *completely* comfortable that would be =
sufficient for the near-pure clay soil that is under the shallow =
topsoil. Somewhere I read that lime can be used to stabilize clay soils, =
and I am wondering if anyone here knows how I can use lime to stabilize =
this soil. I really would HATE to put out alot of work to have my home =
fall down due to a lack of bearing strength under the foundation! LOL! =
If anyone here has any info on how I can stabilize my soil with lime, =
please, please let me know.   :D

  Kim

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<DIV><FONT face=3DArial size=3D2>Hi Kim, you can usually get your County =
Extension=20
Agent or the Univ. of Arkansas Extension Service (you also have ATTRA =
there in=20
Fayetteville) to give you a soil test - you can get the bags they supply =
at the=20
county Extension Office and send them in - the analysis is usually free, =
unless=20
you want to also know organic content.&nbsp;&nbsp;&nbsp; The Extension =
Service=20
also knows the prevailing soil type in your county.&nbsp; Just take a =
sample at=20
the proposed site of your house and send it in.&nbsp; If the clay =
content is not=20
enough, at least you will know what will grow there!!!!! - and they will =
also=20
tell you what amendments need to be added for specific =
crops....Namaste.&nbsp;=20
Happy Holidays.&nbsp; Myra</FONT></DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
  <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
  <DIV=20
  style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
  <A title=3Dkwest at arkansas.net href=3D"mailto:kwest at arkansas.net">Kim =
West</A>=20
  </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dcoblist at deatech.com=20
  href=3D"mailto:coblist at deatech.com">Cob List</A> </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Friday, December 20, 2002 =
9:59=20
  PM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Cob: Foundation =
Strength=20
  Relative to Soil Type</DIV>
  <DIV><BR></DIV>
  <DIV><FONT face=3DArial size=3D2>A while back I made a post relating =
the clay=20
  content of our soil here. A nice fella, I do not remember who it was, =
wrote to=20
  me that there is no way I can know the make-up of our soil without lab =
tests.=20
  Yesterday I found a book that I knew we had, yet did not know where it =
was. It=20
  is entitled "Soil Survey, Ouachita County Arkansas". After a bit of =
time=20
  studying the maps and information in the book, I now have a generic =
lab test=20
  result for our soil. Granted, it was not taken directly from this =
property,=20
  but it was a sample of this soil type.</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial size=3D2>I found that our land is classified =
as Kirvin=20
  fine sandy loam. When this book was published, the classes of soil =
were=20
  standard country-wide. That was in 1973 so things may have changed =
somewhat,=20
  although the description would not change with the class name if =
indeed the=20
  class name has changed.</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial=20
  =
size=3D2>=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2>What follows are some of the =
properties of Kirvin=20
  soil:</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial size=3D2>Depth to seasonal high water table: =
30-60=20
  in.</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2>Depth from surface of typical=20
  profile:</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2>&nbsp;&nbsp;&nbsp; 0-9 in......fine =
sandy=20
  loam........AASHO A-2 or A-4.........30-40% passing #200 =
sieve...shrink/swell=20
  low</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2>&nbsp;&nbsp;&nbsp; 9-55 in....red =
clay,=20
  plastic.......AASHO A-7...................75-95% passing #200=20
  sieve...shrink/swell moderate</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2>&nbsp;&nbsp;&nbsp; 55-73.....silty =
clay=20
  loam..........AASHO A-4 or A-6..........60-75% passing #200=20
  sieve...shrink/swell low</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial size=3D2>Kirvin soil limitations relative to =
foundations=20
  of dwellings: Moderate if slopes are less than 15%; moderate bearing =
strength;=20
  moderate shrink/swell potential; severe if slope greater than=20
15%.</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial size=3D2>As relates to septic systems: =
severe-slow=20
  percolation.</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial=20
  =
size=3D2>=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial size=3D2>Firstly, let me say that the depth to =
seasonal=20
  high water is no problem. We have lived here for nearly 13 years, =
through=20
  near-drought and through high precip years. Where I plan to build is =
atop a=20
  hill, the highest point on the property,&nbsp;and water&nbsp;has never =
been a=20
  problem, even during floods and/or high precip years.</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial size=3D2>Secondly, The clay content given =
above pretty=20
  much agrees with the&nbsp;jar tests that I did. I had said that 6-12 =
inches=20
  down is pure red clay. The lab tests say that 9 inches down is 75-95% =
non-sand=20
  soil. This hypothetically could contain silt, but there are not three =
layers=20
  in my clay samples, only two. After the gentleman drew my attention to =
the=20
  need for a lab test, I did get a magnifying glass and do another =
examination=20
  using it. I found that under magnification the fine sand content that =
wasn't=20
  visible to my naked eye was indeed there. I owe him, whoever he was, a =
thank=20
  you for influencing me to back up and re-examine my samples. Had I not =
come=20
  across this soil survey I may have continued erroneously thinking the =
clay was=20
  pure. Thank you!</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial size=3D2>Anyway, the reason I posted this is =
because of=20
  the previous discussions we have had on rubble trench foundations, and =
the=20
  fact that they have been around a while and work very well. I'm =
wondering if=20
  part of the success of those foundations was because they were set on =
stable,=20
  weight bearing soils. Above, it says the foundation limitations here =
are only=20
  moderate, meaning they can be overcome with good planning, so long as =
the=20
  slope is less than 15%. There is no problem here with that. Where I =
planned to=20
  build does indeed have a slope of less than 15%. My concerns, though, =
is the=20
  A-7 AASHO rating of the soil&nbsp;at 9-55 inches deep. A-1 is gravelly =
soil=20
  with a high bearing strength, and the scale goes down to A-7 which is =
clay=20
  with little strength if wet. If I built on top of the ground I would =
be=20
  working with an A-2 rating which is not bad, but once I dig down for =
the=20
  foundation I will be in A-7 soil which is the worst for weight =
bearing. I know=20
  I've been told "tamp, tamp, tamp...and good drainage is a must", and I =
know=20
  that is a very important part of building,&nbsp;but I am not =
*completely*=20
  comfortable that would be sufficient for the =
near-pure&nbsp;clay&nbsp;soil=20
  that is under the shallow topsoil. Somewhere I read that lime can be =
used to=20
  stabilize clay soils, and I am wondering if anyone here knows how I =
can use=20
  lime to stabilize this soil. I really would HATE to put out alot of =
work to=20
  have my home fall down due to a lack of bearing strength under the =
foundation!=20
  LOL!&nbsp;If anyone here has any info on how I can stabilize my soil =
with=20
  lime, please, please&nbsp;let me =
know.&nbsp;&nbsp;&nbsp;:D</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial =
size=3D2>Kim</FONT></DIV></BLOCKQUOTE></BODY></HTML>

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