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Foundation question

Started by bigshow, March 18, 2008, 09:07:39 AM

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bigshow

Before i do the house, i'm doing a TF garage first...i'm thinking of having the slab for that poured as soon as the ground thaws.  I have a question about how the foundation should be done.  In the picture...the dark brown is a post, on the outside of that is a 2x6 stick wall.  the bulk of the post will not be resting on the 8" concrete stem wall.  No way the floor is gonna take that point load...so, what is the correct way to support the frame?  pour colums down to the extra wide footer that the post will sit on? 


any input would be appreciated....
I never try anything, I just do it.

Jim_Rogers

Quote from: bigshow on March 18, 2008, 09:07:39 AM
  pour columns down to the extra wide footer that the post will sit on?

Yes, this is one solution.
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

bigshow

haahaha ok Jim, i'll bite....any other solutions??
I never try anything, I just do it.

Jim_Rogers

Sure, move the wall in under the post line and cantilever the exterior wall out.

Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Don P

Or, slide the 2x6 wall out 1.5". Draw a 45* line from inside post corner to the 8" wall, it should then be in concrete all the way.

alpmeadow

Hi
Just for interest, is this garage for sole purpose of parking vehicles or will it be a workshop, storage and perhaps a small temporary/permanent living space above the garage level.  I think  any building described as a garage is always used for more than that.  When I built my garage workshop, I had 10' ceiling and 8' garage doors and I wish it were higher now.
Cheers
alpmeadow
Tallis Creek Woodlot, LT40G28,KubotaMX5000

Jim Haslip

Quote from: Jim_Rogers on March 18, 2008, 09:31:07 AM
Quote from: bigshow on March 18, 2008, 09:07:39 AM
  pour columns down to the extra wide footer that the post will sit on?

Yes, this is one solution.
Yes, I would call that a "pilaster" and it takes a bit more concrete and a piece of steel or two, but is quite easy to do, assuming you are okay with concrete forms.

Another method would be to use a dropped "brick ledger" on the exterior (and a bit lower than the floor) to rest the exterior wall onto. This ledger could be cast as a part of the wall and would not need to go all the way to the footings, nor need it be as strong, since the Frame is (should be) taking the majority of the weight of the building. It could be a piece of 4 x 4 x 1/4" Angle Iron, for instance, but I am not an Engineer. This gives the advantage of being somewhat more "sealed" than the pilaster option

witterbound

How about just putting some 2x6's under the post bottom that is hanging off the wall?  Seems like a few 2x6's would be easier and cheaper than forming a pilister, or whatever it's called.

mad dog

                                                                                                                                                    Are you sure you are not Grizzly Adams?
mad dog 78 acres,pasqualli tractor,L-15 woodmiser

beenthere

Quote from: mad dog on March 21, 2008, 09:59:30 AM
                                                                                                                                                    Are you sure you are not Grizzly Adams?

Just out of curiosity, how does mad dog get his posts to start way to the right of the page? 
Is it a 'trademark' ??

??? ??? ???
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

Jim_Rogers

                                                Just lots of extra spaces before you start typing.......
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

mad dog

                                                                                                                                                                   Maybe cause I am left handed?
mad dog 78 acres,pasqualli tractor,L-15 woodmiser

beenthere

That a guess on your part, or is it something else??
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

bigshow

                                                                                I
                                                                                    am
not
                                                                                                        Grizzly Adams.
I never try anything, I just do it.

Engineer

8X8 post, assuming terrible quality concrete at 2000 psi, means each post, in the simplest of terms, could support over 60 tons before the concrete fails.    I can't imagine a barn or garage being that heavy.  The purpose for footings and pads under columns on a foundation is to transfer and spread out the point load of the column on the subsoil.  Typical subsoil loading is between 1000 psf (that's pounds per square FOOT) for typical clays and loamy clays up to around 6000 psf for gravels and gravelly till.  Usually we figure 3000 psf for a "typical" loading in this area.  Your mileage may vary. 

The design may be somewhat dependent on how you plan to pour the slab.  If your slab will be poured entirely within separate frost walls, it looks like you will have the posts sitting on the seam - if so, NOT good.   If you over pour the slab on the walls, you will probably have no issues.  The best way to pour and still have plenty of bearing is to pour both walls and slab monolithically - basically an "Alaskan" type slab with extended feet.  You would form one side only, the outside of the wall, and use the soil itself as a form for the inside of the pour.  You will probably use a little extra concrete, but a careful excavator will minimize that.  Then, you can angle the inside of the dirt "form" so that you have a load path from the end of the post, downward at a 45 degree angle toward the outside of the wall, to the footing.  That gives you some additional concrete under each post and you don't have to do the whole wall that way, just a very rough "pad" at each post location.

Or - you could cantilever the wall....  ;D

FYI - A typical compact car produces 20-40 psi depending on tire pressure and the weight of the car.  Just so you see the difference.

Jim Haslip

What about a 'thickened' edge slab directly under the post locations?
Maybe twice as deep as the basic slab with rebar dowels and a 'mat' of rebar to tie the thickened edge into the wall, then pour the slab over the walls?

Dave Shepard

Engineer, I've been through Shaftsbury, your subsoil will support about 4.2 million psf. Makes nice countertops when sliced thin enough. :D I like the Montclair Mariposa the best.  Danby Marble


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

snowman

bigshow heres my advice, get a haircut! :D Actually I don't look much better, took my wife out to dinner last night and she insisted on cleaning me up first. WOMEN! ::)

bigshow


"bigshow heres my advice, get a haircut!"


oh man, that wouldnt be very 'metal'.
I never try anything, I just do it.

mad dog

Quote from: bigshow on March 21, 2008, 02:48:05 PM
                                                                                I
                                                                                    am
not
                                                                                                        Grizzly Adams.
[/quote                                                                                                                                                 ]Sorry if I insulted You Bigshow,mad dog,Some people call Me Ralph Mouth They think I look  like him
mad dog 78 acres,pasqualli tractor,L-15 woodmiser

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