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shadetree 09-01-2011 12:41 AM

Replacing support post
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Replacing support post

The back storage addition to my new home has a post supporting the central beam that worries me. The post 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 wood above it to become noticeably compressed.

The plan is to support the beam (3x 2x12s nailed together, warped slightly in the 13ft section due to the post initially being placed 15 feet from the right wall) above with two temporary jack posts while the old post is removed and for the week or two while the new pillar is curing. The new pillar is planned to be 12x12 brick pillar filled with cement and an central threaded reinforcing rod that is secured into the slab. I was planning on using concrete brick instead of masonry brick for cost reasons.

Due to the beam being warped, I was planing to reinstall the old post that is removed with a new cap about 5 feet from the right wall to help reduce stress on the beam and eliminate the 13 ft stretch.

Some questions:

What would make good cap material for the brick pillar to distribute the load? I was thinking a single 2x12x12 with the wood grain perpendicular to the beam.

Are there any structural reasons to use wood or metal for support instead of brick? I do not live in an area with earthquakes. Any issues with using concrete bricks instead of masonry in a structural situation like this?

What would be the best way to lift the beam enough to remove the old post? Planning to get a 12ton bottle jack and a 4x4 to lift with, placing the jack on the side of the post with the longer span, and just keep tightening the jack posts up as it's lifted the 1/4 or so until the post is free.

Any input would be appreciated, and have a safe labor day!

BridgeMan 09-01-2011 01:38 PM

Your plan sounds like you are making more work for yourself than required, with a potential for questionable results.

Do you have some good reasons for using "concrete brick" (we've always called them slump block) with a core of reinforced concrete, instead of a single member column, such as steel pipe?

Trying to get good concrete consolidation inside of a brick shell won't be easy, and access for bringing concrete up to bear against the beam will also be problematic.

Bottle jack/post idea is not the best, as it is more susceptible to buckling during setup and use, leaving you with some serious problems when it goes.
Much better to use a simple screw jack post, consisting of nesting pipes, with a top threaded steel pin and bearing plate. Bought mine on sale at Home Depot for less than $20 each. The double pipe arrangement makes them adjustable, using small steel pins that are included.

Quick and easy way would be to cut existing pipe at the floor (after weight is taken up by temporary support) using a large angle grinder, then shifting it to the desired location with a steel shim plate of appropriate thickness (half-inch or so), followed by welding the plate to the pipe.

Entire operation could be done in a few hours, half a day at most.

shadetree 09-01-2011 03:25 PM

Mostly cost, availability and ease of use. I can pick up concrete bricks for around 30 cents each and get the whole pillar built built for about $60. I have no welding equipment, nor a proper grinder (I use a friction disc on a circular saw for cutting metal). Austin also has few metal yards, and I didn't have the best of luck with them trying to find steel sheet to use as a radiant barrier when I was installing my wood-stove (built it with cinder-blocks instead). I also have brick support columns holding up my carport, so the brick here might look better too. I was planning on using concrete bricks, something like this 7-3/4 in. x 2-1/4 in. x 3-3/4 in. Concrete Brick-25100130 at The Home Depot Not the grey hollow cellular cinder-blocks.

I didn't know you could use the jack posts to lift as well. That will save alot of headache as I was planning on buying a pair anyway! Something like Tigerbrand jack posts would work?

nealtw 09-01-2011 04:24 PM

All lumber has a crush facter and if your house is 1 year old, what you see is what you get! How big is the beam, what is it carriing and how big is the post? How do you intend to spread that load with your temp. support? If you are planning on moving the support post are you planning to underpin it?
We do this work all the time and could plan it in my sleep and I alway have a plan, the one the on site engineer wrote.

shadetree 09-01-2011 09:17 PM

The beam is 3 2x12s nailed together, it's 25ft long. The post is 83" from the foundation to the bottom of the beam and is 3" in diameter.

I wasn't planning on altering the slab below the post in it's new location as being only 5ft from the end of the girder, it would be carrying considerably less weight than it is now. I also don't believe the foundation is significant in any way directly under the post in it's current location; by looking at marks on the girder, the post seemed to originally be about 2 feet away from where it is now.

nealtw 09-01-2011 09:43 PM

Where ever the post is it does carry 1/2 of the weight above. If you say it fast you would think tyhe post should be in the center of the beam. The question is how the house or roof is constructed above this area. The foundation is designed to take the load of the house. If you were to to dig it up you would find extra sqaure of concrete at each end of the beam and a square of concrete where this post was to go. The floor cannot take this load with out extra support. Is the post bolted down and is there evidence of that where you think it was moved from.
Evan if you find that, some one may have corrected an earlier mistake.
You really need an engineer to look at the house.

shadetree 09-01-2011 10:58 PM

The post in it's new position seems like it would be carrying less weight because most of the load would rest on the pillar that is going where the post currently is now (near the center of the beam). I'm planning on going from the 1 post that is there currently to 2.

There is no evidence that the post was ever bolted down in either place.

What information would an engineer be able to tell me?

nealtw 09-02-2011 01:49 AM

He would calculate the weight of the house and the load barring on that post and how best to spread that load to do your temp lift without breaking the floor and if your second post should carry load or just be a dummy post.

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