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Building your own headers

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Strouty

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When you build a header is there a way to figure in how much extra strength a piece of plywood will add? Example of what I am thinking is if you take two 2x10s and sandwich a piece of 1/2" plywood between them, I know it will be stronger than two 2x10s, but how much stronger?

I am getting ready to do a few changes at the house and I would like to have a little understanding of what is needed. None of the span tables even discuss this method, but I have used it for all my headers over doors and windows.

I will have the local lumber yard price out LVLs since they will have the engineer check on what is needed for the span. If it was just a short span I would overkill it and be done. I have two separate 10' (ish) spans and there is living space above it, so I don't want to eff around.

Any input would be great.
 
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srmofo

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I always ignored it, as most of the time we added the ply to make the header the same thickness as the wall. Use the calculations for the 2x only and the ply will just be a little more safety factor.

That said I dont do this regularly, so take it for what its worth
 
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sublimate

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Damn, I clicked on this thread expecting to see pics of gorgeous TIG welds on mandrel-bent stainless tubes. Buzzkill.

Sorry, I'm no help.
 
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Scott65

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I would opt for the LVL's- more stable than 2x10 lumber and they will not flex. You will pay more, but for that span piece of mind is the most important factor. Last time I used conventional lumber I sandwiched a 3/8" steel plate between the prices of lumber And bolted the whole thing together.
 
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Strouty

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Sorry guys, I would have put tig welded steel headers under fabrication section.

John, I had never heard of the name flitch plate, but I have seen them. Thanks for the link, now I have some reading to do.

I always used the plywood as a dimensional spacer, but I would glue and screw it too. I guess that makes for a nice safety factor, I just figured it would probably actually end up being close to the equivalent of three 2x10s if done that way.

Once the engineer gives me the LVL size can I back track and figure out how much of a regular beam I will need? It may be that the LVL is going to be cheap enough that I won't care, I just know that I have some materials all ready and would prefer to use them rather than buying new if possible.
 
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A_Pmech

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Strouty said:
Once the engineer gives me the LVL size can I back track and figure out how much of a regular beam I will need? It may be that the LVL is going to be cheap enough that I won't care, I just know that I have some materials all ready and would prefer to use them rather than buying new if possible.
Click to expand...

You could, but in that case why hire the engineer if you're going to do his work for him? :)
 
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Strouty

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A_Pmech said:
Hmm. I'd ask them to show their work.

:lol:
Click to expand...

That is how they sell them to people, you get the company engineer to check loading based on your information, but you don't get to see the work. I bet they would give you a copy when you buy the beams.
 
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Strouty

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I know they take some time to do it, I had them ask me all kinds of extra questions before they would give me the header size on my garage. I asked for beams that would support a second story in the future and they needed to know what the use was as well as how tall the building would be and a bunch of other information. I was impressed at how thorough they actually were.
 
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MN4x4

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x2 on LVL's. Also, they are 1-3/4" thick, so two of them is a perfect match to 2x4 walls.
 
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Falcon67

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Mandrel bent LVLs with HPC coating 34" equal length 3 1/2" collector with plywood gussets. I'm so confused.

Actually, the 1/2" of ply in a header is just there to make it the right thickness. Two 2x? is 3" thick and you need another 1/2 to make the unit flush with the trimmer 2x4s. Now if you are talking about something like my 16' garage door header, I used two 2x12s with 1/2 ply insert, lots of construction glue and 16 penny nails. I'm sure the unit was stronger than just two 2x12s but by how much I can't say. It's holding up fine, FWIW.
 
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Strouty

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It is interesting that there are no structural tables on adding plywood. I know it has a lot more strength, I also know people add it to make it the proper width. I just wish there was some more data readily available.
 
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lotsoftools

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I always thought it was added to make up the width. I know I've skimped on a couple of doorways when I didn't have a long enough piece to fill the whole space.
 
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larry_g

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Strouty said:
It is interesting that there are no structural tables on adding plywood. I know it has a lot more strength, I also know people add it to make it the proper width. I just wish there was some more data readily available.
Click to expand...

I would suspect that there are no tables available because there is a wide variety of plywoods available from **** to very good. Dimensioned lumber has had a lot of testing and history to be able to develop strength tables.

lg
no neat sig line
 
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Falcon67

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There are no tables because the header is sized to the load/opening, span and type of structural lumber. You would not downsize a header because of the ply.
 
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rippered

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I took a building trades class in place of my senior year of high school at the local vocational school. They taught us to make strips of Plywood to make the 2x12 or 2x10 the correct thickness. The 3 different companies I framed houses for all did the same thing. We did use LVL and other materials as beams and headers also but usually it was 2x12s.
I haven't been a framer for 10 years and we all know techniques/codes change.
 
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Stuart in MN

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I've seen where the two 2x pieces are nailed together without a plywood spacer, which then leaves enough space for a piece of foam insulation. It doesn't provide a lot of insulation but it's better than nothing at all.
 
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