New member from Texas - foundation questions

Started by muldoon, February 13, 2008, 07:40:32 PM

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muldoon

Hello,

What a great forum you guys have here.  I have been reading and lurking for several months while I look at and think through all of the great projects underway and the ideas being discussed.  I remember my wife was pretty frustrated when I was up late on christmas eve reading this forum.  Great job guys.  :)

Anyway, I know there are many posts on foundations already on this site, and I have read most if not all of them.  However I want to post my situation and get some opinions from others before I do something foolish like begin buying the wrong materials. 

I am looking to build a 1.25 story (two 8 foot storage lofts on the ends) 16' x 40' on a raised beam foundation.  I like the sonotube approach the best particularly the approach taken in http://www.countryplans.com/wing.html

However, I would be looking at 3 rows of 5 piers.  Each  row being the 40' span, with each pier being 8' apart.  The sonotubes I would bring above grade about 6 incles and place a 6x12 (maybe 4x12?) buildup beam on top.  But .. some questions remain. 

The good news is I am in central Texas and have zero frost line.  I have very minor slope, between 1 and 3 degrees (level but water has a place to go - which is about 75 yards away to a pond), no ground water anywhere near the first 50 feet, drainage is very good although after heavy rains there are some puddles for a few hours.   Last piece of good news, no building code, no inspectors, no county or city to ask.   Unfortunatly that last bit means I also dont have anyone to really look it over and approve it either.  So, the bad news is high clay and sand soil and high susciptibility of expansion as we get monsoon rains and summer droughts. 

Here is my soil details. 

From 0 to 7 inches   - fine sandy loam
From 7 to 17 inches  - clay  (dark brown clay with yellowish brown mottles)
From 17 to 24 inches - Clay and loam (clay with grayish brown ped interiors)
From 24 to 33 inches - clay and sandy loam (gray and white sandy clay loam with yellow mottles)
From 33 to 55 inches - white weakly cemented tuffaceous sandstone (bedrock?)

Shrink/swell or expansive soil is the problem.  Given this data, what method would you guys  recommend  to approach this task?  I dont want my piers to come heaving up from the clay expansion, so what can I do to mitigate this?  How deep should these tubes go? how big of tube? What size footing to rest on?  Which bracket to use for mating the beam to?   What if anything can I do to get out cheaper?  Those kinda questions. 

Thanks again, I am looking forward to participating in this forum. 

Redoverfarm

 w* Great place isn't it.


Quote from: muldoon on February 13, 2008, 07:40:32 PM
Hello,

From 33 to 55 inches - white weakly cemented tuffaceous sandstone (bedrock?)


I think you have answered your own question IMO.  Be sure to take plenty of photos of it's inception and keep us updated on your progress.

John



n74tg

Where in central Texas?  I grew up in Mexia.

Okay all you out of staters.  Try pronouncing Mexia.  This should be interesting.
My house building blog:

http://n74tg.blogspot.com/

MountainDon

Just because something has been done and has not failed, doesn't mean it is good design.

muldoon

n74tg: I live and work in Houston, but purchased the property in Muldoon, TX population 446.  It's south of La Grange about half way to Flatonia off 609.  If you are aware of the locations of Houston, Austin and San Antonio find the spot that is nearly in the middle of them all.  That's roughly it. 

redoverfarm:  I was afraid someone was going to say that.  I was really excited about no frost line too.  It will some shovel and post hole digger work for me it seems. 

Anyone else:
I have never used any pier/post and beam of any type.  If anyone has any suggestions for the other questions I asked (size of tube, size of paver/block base under the tube, simpson connector (I really like the idea of an adjustable nut for a few inches of adjustment like the EBT44T as discussed elswhere in this forum, but they don't seem to make this in 6x, only epb66 with an 8 inch pipe elevation that requires being fixed in place).   

can't resist...  muhh - hay - uhh


Redoverfarm

If you have viewed the site before then you know that if you ask a question that someone will "throw a monkey wrench in your works" so to speak. But in a good way.

I believe that with that much foundation work you had better be finding a piece of mechanized machinery or buy stock in a glove company and stock up on the Advil ;D

NM_Shooter

"Officium Vacuus Auctorita"

MountainDon

One good thing about his ground is it doesn't seem to have a bunch of large rocks to mess with as the ground is excavated/drilled. I hope I'm not wrong on that.  :-\
Just because something has been done and has not failed, doesn't mean it is good design.

ScottA

I did a job in Mexia once. A State school. That's Ma-hay-a. I'd go to bedrock with those piers.


n74tg

Yes, it appears my "Mexia pronunciation" challenge was in fact a hijacking of the thread...sorry about that. 
My house building blog:

http://n74tg.blogspot.com/

glenn kangiser

I think I would just get the bases down to the bedrock type layer- sono-tube up -- gravel fill around - Ideally trench to drain downhill from all of the bottoms of the footings.

I would also consider ease of adjustment incase anything shifted.  Adjustable stumps as Jonesy called them -- bracketed on all thread with a nut to readjust = probably 3/4 min. dia.  1" would probably be better. 

...and Welcome to the forum.
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.

Redoverfarm

Don't loose any sleep over it. It happens quite frequently. It usually finds the trail back to the original subject.