Author Topic: Pier foundation  (Read 5839 times)

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Offline windrift

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Pier foundation
« on: October 25, 2008, 04:56:42 PM »
I have the enchilada kit.  I am planning to build the 14x24 little house but have quite a few questions.  I would like to make the taller wall and extend the loft room as in the builder's cottage.

First, my soil should support 4000 lbs per sq ft.  It doesn't really hold a ball shape when wet but I am trying to err on the safe side.  I don't have any code requirements to conform to.  One thing of concern here is high winds that sometimes cause shifting on a post and pier foundation (so I've been told).  Quite a few houses here are just built on concrete blocks.

I want to use the deep pier foundation but only need it to be 12" down since that is the frost line here.

Can I extend the columns up 2 ft to create the crawl space?

Will 8" columns be fine if I do?

If so, do I need to use rebar or some sort of reinforcement?

How difficult is it to level these columns?  Use a string line and line level?

Will I need to make a footing for each column or is gravel adequate?

Can I inset them so I can make a rock wall to enclose the crawl space later?


John_C

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Re: Pier foundation
« Reply #1 on: October 25, 2008, 05:22:14 PM »
 w* to the forum

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One thing of concern here is high winds that sometimes cause shifting on a post and pier foundation (so I've been told).
 
Properly built that wouldn't be an issue.  In many hurricane areas variants of the pier foundation are the preferred method of construction.

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Quite a few houses here are just built on concrete blocks.
  Just stacked on the ground??? or column blocks on a footing poured with steel??... big difference!

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I want to use the deep pier foundation but only need it to be 12" down since that is the frost line here.
I'd go at least 18" if you are concerned about wind induced shear forces.

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Can I extend the columns up 2 ft to create the crawl space?
Probably but if you want a crawl space, why not build a crawl space foundation?  By the time you extend the columns and enclose between them it will be nearly as much work for an inferior crawl space.

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Will 8" columns be fine if I do?
Given the wind - shear load you might want to consult with an engineer.  an 8" poured sonotube with some steel is pretty sturdy.

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If so, do I need to use rebar or some sort of reinforcement?
Given the wind - shear load I would.  The amout of steel you would use is very cheap insurance.

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How difficult is it to level these columns?  Use a string line and line level?
That way lies madness.  Use a plastic tubing water level.  There are several posts on the forum about how to DIY one.  Mtn. Don gave a good description a while back.

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Will I need to make a footing for each column or is gravel adequate?
Given the wind - shear loads I would use a 2' x 2' x 8" pad beneath each column.

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Can I inset them so I can make a rock wall to enclose the crawl space later?

Answered above

As always YMMV
Good luck


Offline glenn kangiser

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Re: Pier foundation
« Reply #2 on: October 26, 2008, 04:13:06 AM »
All of what John C said....

Tall cols could be pretty unstable without the bases. 

As John suggested, you may as well enclose it now if you plan to later and you mentioned rock wall so maybe you could do a rubble wall with rocks and grout poured between them - reinforced piers in their proper locations.
"Always work from the general to the specific." J. Raabe

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John_C

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Re: Pier foundation
« Reply #3 on: October 26, 2008, 04:30:39 AM »
I've been working on a neighbor's house building new stairs and a porch extension, all supported on 6x6's.

He had collected some used 5 gal. buckets.  We cut the bottoms out, turned them upside down, oiled them,  & used them as molds for the piers. It worked well if they are tall enough.  The guys who tape drywall often throw away lots of 5 gal buckets.  Sono tubes have gotten pricey.

Offline John Raabe

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Re: Pier foundation
« Reply #4 on: October 26, 2008, 05:34:08 AM »
Yes, I agree with all that is said here. I would go lower than the frost line (to get better anchorage to the ground) and do a poured footing with rebar that are extended and tied back into the vertical bar in the concrete pier. The rule of thumb for a footing is thickness = 1/2 the width. This can be thinner if you lay down a mat of rebar.

Here is more info on construction and leveling: http://countryplans.com/foundation/index.html

You could inset the piers from the end of beams a foot or less as shown in the Little House plans if you want to do a rock wall skirting. However, I think you might be better off to consider a poured concrete perimeter foundation - if only because you can do a far better rock faced foundation if you have a real wall to attach to. The superior critter proofing and wind anchorage such an option provides is then a free bonus.

Look at the types of stone walls the Nearings (Helen & Scott) built in their projects. Maybe that could be used for you stone faced foundation. Here is an introductory article I found with a simple search: http://www.i4at.org/surv/rockwork.htm
None of us are as smart as all of us.


Offline windrift

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Re: Pier foundation
« Reply #5 on: October 26, 2008, 07:45:05 AM »
Thank you for the good advice

O.K. stone wall not worth the hassle

More technical information: This area ( Arkansas ) has 3 second wind gust factor of 90 mph.  Maybe the cheapo pier version foundation would be adequate?  What if I decided to make 2x6 walls?  Still O.K.?

I can't get trucks into my site for a poured foundation.

They actually do just stack blocks up and build a little house down here.  Numerous people are telling me that the columns are overkill for this little house.  One recommendation: blocks for 4 corners and 1 in middle.

I have asked questions of numerous local people and get a variety of answers.


Well, thank you for helping an ignorant person meander through these ideas.

Wendy

Offline glenn kangiser

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Re: Pier foundation
« Reply #6 on: October 26, 2008, 11:43:36 AM »
Some of the local methods may work but for piece of mind the piers should likely be minimum. 

Lot of people get away with lots of things for a long time but a solid foundation is your best insurance for longevity of the building.
"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.

 

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