Sandwich a beam

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abunaitoo

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Not sure if that's what it's called.
I have a beam over the garage. 20 feet long
It was extended a while ago be adding a beam under it.
It was sagging, so we put a post in the center of the span.
The post has to go. It's always in the way.
Friend said he has added 3/4 ply to both sides of beams to straighten and strengthen them.
Plan is to nail/glue two layers on both sides of the beam.
Much cheaper than replacing the beam.
Sound like a good idea?????
 

Eddie_T

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I made a sandwiched load bearing beam for a 16' garage door. It was so long ago that I don't recall the details but it has stood the test of time.
 

Sparky617

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First, I'm not an engineer so my free advise may be worth what you're paying me for it. Plywood is available in 8' lengths, so while I think it could add some strength to your beam, I don't think it'll be enough. What is above your garage? Attic or living space? I'd probably jack it up to be level, sandwich the plywood with a piece centered over the 20' length with pieces on either end, glued and screwed. Then I'd add a LVL for added strength or a 2x10 2x12 whatever is there now by 20' glued and screwed to the existing beam. An LVL would be stronger than 2x stock.
 

Snoonyb

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Plywood is available in 6, 8,10, and 16' lengths, with prices comparable.

Utility grade is standardly available in 10' lengths.

I'd jack it up to level, or slightly crowned, and then add the repair, glued and screwed.
 

tomtheelder2020

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About 25 years ago, I did exactly what you plan. Snoonyb is exactly right - jack it up to a slight crown. I didn't and it immediately sagged. Much better than it was but not as good as I hoped. Some sag since then but not too bad. I used 8-ft segments of 1/2-in plywood, 3 layers on each side of beam, with butt joints staggered as much as possible, glued and nailed.
 

Steve123

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Might work if you put a steel plate under the plywood. That would be called a Flitch Beam.
You would still want to put wood over the steel --- the wood over the steel prevents the steel from buckling.
 

abunaitoo

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Thanks to all.
He wants to use 3/4 ply on both sides.
Two layers and staggered.
Only thing above it is the solar water panels.
Water is heavy.
Plywood is ridiculous right now, but that pole is driving me crazy.
He said ACX.
Recommendations ??????
 

Hamberg

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Wait!! Beam(s) were sagging and you think not replacing them, BUT sistering them with plywood, is somehow going to "fix" the problem!?!

Like @Sparky617 said, I am not an engineer but if a LOAD carrying beam (rafter) is sagging, no amount of sistering is going to cure the problem!

Typical snow load weight in the Northeast is ~40lbs per sq ft. (unfrozen) Water is ~60lbs per sq ft PLUS the weight of the panels. From that you are describing the beam (rafters?) where never doubled-up to start.

(Logically) if it were me, I may enlist the services of someone/anyone who could verify my roof/panels won't end up in the living space, at some point.
 

abunaitoo

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Just one beam.
Solar has been up there for over 25 years.
It's the only thing on the roof.
Nothing under but the garage.
Water doesn't freeze here. No snow either...................at least not yet.
 

mabloodhound

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I would add a steel plate the full length (flitch) and bolt it to the beam, top and bottom edges every 16".
 

Eddie_T

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I can't picture what the beam is supporting.
 

Eddie_T

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It was extended once by adding a beam under it. Doesn't that affect the fix? I think the existing "beam" needs more definition (maybe a pic) before any fix is suggested.
 

billshack

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I remember working on a large renovation and they wanted to take out a bearing wall, they called for an engineer that designed a steel i beam and them we all sweated to install it in and existing house very difficult. at the end the engineer came by to inspect it. and said it was good. there was a very skilled old carpenter on the job and he told the engineer that he could have done the same thing with plywood glue and screws, the engineer fully agreed with him. So go ahead and install several strips of plywood and glue a screw it together .
 

abunaitoo

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Would it better to screw or nail it????
What kind of glue would be the best????
The pole is just in the way.
Only reason it's there is because of the sag.
But it just has to go.
 
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