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shadetree 09-15-2011 02:39 PM

6x6 wood post vs. brick pier vs. cinder-block pier
I'm replacing a homemade (previous owner) 83x3.5 steel post in my garage that is out of alignment, with the bottom of the post about a half inch offset from the top. In addition, the post cap is far too small for the load it's carrying and is causing the 25ft girder (3 2x12s) above it to become slightly compressed.

I've tried searching for new lally columns in the Austin area, and they just aren't available here, so I'm left with 3 options: A 6x6 wood post, a concrete filled 12x12 brick pier, or concrete filled 16x16 cinder-block pier. All would be affixed to both the 12 thick slab & girder.

I'm leaning towards the brick pier as it seems robust and would take up a smaller footprint than the cinder blocks, and I also have 3 12x12 brick piers holding up my carport, so it wouldn't look out of place; but the cinder blocks would be cheaper and easier to construct. I'm concerned about how much load a 6x6 post could accommodate. Any suggestions on if one would be better than another?

A note on lally column availability: I've been searching for the past 2 weeks for lally columns, I've called a dozen steel yards, several steel fabricators, many building supply companies and HD/Lowes, none of them had heard of lally columns. When I described what the columns were, not one of them sold them. I've given up the hunt at this point, pretty sure the lack of availability is why the sub-par lally was used in the first place.

Ron6519 09-15-2011 03:56 PM

That's very odd about the column search. It's like saying, I can't get a hold of a 2x4 around here.
In switching them out, you just need to make sure the new one has the capacity to hold the load. A larger column, might require a larger footing.

Daniel Holzman 09-15-2011 04:06 PM

Any of the three options you describe can certainly work. All of them require a proper footing. You said you had a 12 inch thick slab, that seems unusually thick, is it perhaps prestressed concrete or post-tensioned? Or are you sure it really is 12 inches thick?

In any case, removing and replacing a column requires adequate temporary support of the girder. No need to remind you that failure of the temporary support can be fatal, so you need to make sure that the temporary support posts you use to hold up the main girder while you install the new post are RATED for temporary duty in a critical support capacity. There are many ways to properly support a girder on a temporary basis, no doubt the same steel yard that has never heard of a lally column has never heard of temporary steel supports, but hopefully someone has, and can supply you with safe equipment.

Tscarborough 09-15-2011 07:04 PM

We don't have basements here, hence no lally posts. Brick sounds like your best solution unless you want to have a tube column made for you, and jack it into place.

JoJo-Arch 09-15-2011 08:02 PM

Colums, colums everywhere.
Suggest you get a structural engineer to look at this. You don't want to end up in hospital or worse, a name on a plaque. The loads you speak of are substantial and disturbing the existing support in trying to remove it without proper temporary backup will result in catastrophic failure. You must take appropriate precautions, and this is not a rule of thumb exercise. The structural engineer will not only tell you what's wrong with the existing structure but what you need to do to make good.

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