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Discussion Starter #1 (Edited)
Sorry for the text only description. I will try to get some pictures or make a drawing if it's impossible to understand.

I have an old garage (1940s) that went through a renovation 15-20 years ago(?) that increased its size by about 50%. They did a decent job, but just one thing - when they took out one of the bearing walls for the ceiling joists to build the garage out, they attached the now unsupported ceiling joists to a new joist that runs perpendicular to them (parallel to how the removed wall used to run) and bears on the two end walls. So this one joist, which is a 2x8 (the rest are 2x6es) supports the new part of the roof (roofridge of the new part of the garage is also perpendicular to the old roofridge, like a dormer but larger) and supports all the joists of the old part of the garage. This 2x8 joist covers a 22 foot span, is made from two 10' pieces with king and queen posts emanating up from the middle, secured with plywood gussets. It is sagging about 2 to 2 1/2 inches in the middle.

Just asking for some ball park opinions. How big of deal is 2 to 2 1/2" deflection? And is this something you could address with a properly installed post, or is it more serious issue than that?
Thanks for your time.
 

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Yes, that much sag in a short period of time is not good---

They really undersized that member----support posts will be needed or a properly engineered lam beam to replace the mistake 2x8 one.
 

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Discussion Starter #3
Thanks for the reply oh'mike. As a quick followup question, and I know that we are still speaking in generalities, if I were to go with a properly sized lvl beam, could I sister the 2x8 to it, or would replacement of the 2x8 by the lvl be better? Thanks again.
 

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I'd need to see a picture of the existing---It could be done either way----the Lam beam could be used to hold up the existing 2x8 --or hanger the joists---need to see which would be most efficient.
 

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Discussion Starter #5
Ok, I took a few pictures to explain the situation better, but unfortunately I discovered that things are a bit more complicated than I realized. More on that at the end the post.

Picture 1: Original structure is on the left - addition is the part on the right with the overhead door and the perpendicular roof line.

Picture 2: The sagging joist. It occupies the same plane as the removed wall of the original garage. You can see it supports the ceiling joists (13' long, 2x6) and the roof rafters of the original structure, as well as its share of the new roof.

Picture 3: The sagging joist is made of two members and a king post, joined midway with plywood, and also supports bracing.

Picture 4 & 5: Two different views of the sagging joist, the old roof supports, and the new roof over head.

New complications: Because of the way the roof is built, and slopes, there is almost no room to install a lam beam on the top plate, and there is insufficient clearance to support it underneath with a beam (if that's even a possibility). So I am back to considering a single large post, but there are complications there as well.

The joist is sagging most at its halfway point where it's joined together, which is also the midpoint of the garage, but the double overhead door is offset because there is a man door beside it, so putting a post at the lowest point of the joist would make it difficult, but not impossible, to park two cars in the garage. Is there any way the joist could be properly supported by a post a foot or two off center? Moreover, will one post be enough? and how do I go about figuring out the best size? Thanks for your time.
 

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I wish I was there---easier to do than to evplain.

That was poorly thought out and poorly executed.

The roof trusses that are hanging off of thet 2x8 need hangers--right now,only nails are supporting the roof structure.

After adding hangers (using short hanher nails)--add the LAM beam behind the existing sagged member----then you need to block it so it will not roll over--

Next comes jacking the roof back into place.

I would build a 'Jack Wall'----this method is safer than any other--wastes a lot of 2x6s--but you could reuse them for another project.

Let me see if I can find a post about Jack walls.--Mike---
 

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Discussion Starter #8
Thanks Oh'Mike. Your explanation plus my additional research is starting to really make it clear to me how to approach this. But I have a couple more questions.

Does the lambeam need to bear on the top of the walls, or does just get fastened to the 2x8 to keep it straight? Would you bolt it or nail them together?

Someone else suggested using 3 of these jack posts to raise the joist back up to level.
Any thoughts on them?
http://www.amazon.com/Tiger-Brand-Steel-Beams-Gauge/dp/B001B1AMNW

Thanks again for your time. It's much appreciated here.
 

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They need to rest on the top plate of the wall--or have posts at the wall that bare down to the foundation.

Those adjustable poles are not great at lifting---the adjustmet screw is to corse--

A jack wall is cheap and stable---you will be lifting the roof--that is a lot of weight--
 

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It has been aa long time (1983), but i built a three car garage with a wall separating one bay. To span the 16 feet or thereabouts, I had to make a beam that was two 2x somethings (I can't recall) with a piece of 1/2 inch plywood sandwiched in between the two boards. Lots of glue and nails later, we had a beam that would span the opening.

The guy from the city planning department was the one that gave me the instructions on what was needed before he would approve the plans. We also had to make a couple of changes to our bracing for the rafters. That garage has been through several storms and hurricanes and is still standing today.
 
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