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Old 02-06-2012, 09:36 PM   #1
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Shed Support Problems

I have a 10' by 20' shed/workshop behind my house. It is a nice building and is actually finished (was formerly a hot tub house). Right now the whole thing is supported on two 4 by 4 "beams" running the length of the shed. Each beam is supported by concrete filled steel piers. Pictures are attached of the current arrangement.

The piers seem strong enough, but the 4 by 4s are way undersized and the floor is really bouncy (which is probably why it isn't a hot tub house anymore). I'm mulling the options to fix this, anything short of pulling the shed off and redoing the whole damned thing would be preferred. Here are the options that I am mulling. Any thoughts and other ideas would be welcomed.

1. The temporary, cheap, band-aid fix would be to install a treated 4 by 4 column under the sag between each steel pier, on top of a precast deck footing, and linking the column to the beam with a strong-tie.

Once installed I would put some cross-bracing on the 4 by 4 columns. This would be an improvement over what is there, but I don't know how long this would last here in frost country.

2. Plan 2 would be to shore up the structure, trim the steel piers, and replace the 4 by 4 beams with doubled 2 by 10s. The beams would be supported using post caps like this:

Some bracing would be required for the new beams.

The wrinkle with this idea is that the steel piers are 2.5 OD, and I suspect that they are actually electrical conduit pipes . There is some strapping currently holding the steel pipe to the beams, but it looks like a homebrew assembly.

3. Plan 3 is to pour 12 footings (3 rows of 4, down the middle and the sides), install new beams on 6 by 6 columns with cross bracing. The only things preventing me from doing this are the thought of digging 4 ft holes for 12 sonotubes in the 2 ft headspace under the shed. Also, the shed is currently non-comforming (it is too close to the neighbor's fence) and so I want to keep the construction activity to a minimum. The neighbor on that side is a bit of an %#^&.

4. Down the road, when I am rich , I'd like to crane the building off to the side and pour a stem wall in the appropriate location. This isn't going to happen soon, unless anyone has some magical ideas or I hit the lottery.

I was looking at doing plan 1 this spring, unless there is some way to do plan 2 with the current steel supports. Plan 3 makes my back hurt just thinking about it. Any thoughts or suggestions?
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Old 02-06-2012, 09:58 PM   #2
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You could always do option 3 or something very simalar with pre-poured piers depending on how soft the ground is. If the ground is too soft for pre poured then it wouldn't be that hard to dig.

I would probably run 2x6 across from 4x4 to 4x4 using joist hangers (unless they are above those 4x4s and I just cant see them), then install one 4x8 beam down the center. You have room to dig holes and use sonotubes at both ends, then install 2 prepoured piers under the beam in the middle


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Old 02-06-2012, 09:59 PM   #3
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I'm surprized that building has not came down already.
4 x 4's have almost no side load strength, if they were used there should have been at least 4, not two, used to spread out the load.
Your beam idea will work but use doubled up 2 X 8's instead of another 4 X 4. It will be far stronger.
I'd be using pored 24 X 24 X 4" thick piers with rebar in them to spread out the load and not sink into the ground. A simple support would be short lolly coloums.

That building could be lifted with two Farm Jacks so those 4 X 4's could be replaced with 4 X 6's for added strength, but do not leave them hanging out like that. Cut them so they end under the siding so waters not hitting them.
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Old 02-07-2012, 12:00 AM   #4
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Plan 3-B:

1. Place flat, with the help of a dolly, 12 unopened 90# concrete bags, at the spots where you think (erroneously) that you need sonotubes.
2. Poke some holes with a nail on the concrete bags, and flatten level their tops with a chunk of 2x4.
3. Come back in a month: you will have 12 rock-solid concrete footings.
4. Set posts on your footings, they'll go nowhere. If fastidious, you can cut a small square on the center of the bags during step 2 and dig in some metal post bases on the concrete bags.
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Old 02-07-2012, 08:40 AM   #5
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Originally Posted by conspikuous View Post
I would probably run 2x6 across from 4x4 to 4x4 using joist hangers (unless they are above those 4x4s and I just cant see them)
There are 2 by 6s running crosswise above the 4 by 4 beams for the floor.
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