For a normal door or window header, standard constructio is a doubled 2x with 1/2″ ply in the middle. I always thought that the ply was to make the header the same thickness as the studs. Right? Or does the ply add a significant anount oif strength? Just curious.
I’m sorry, I thought you wanted it done the right way.
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Replies
Ed, when I was framing for a living..we often used strips of ply for "packers"..no added strength.
I guess if ya PL glue a full swath, yer getting more strenght, but to be honest, I'd adopt a box with insul in todays time. Thank you Mike Smith.
Spheramid Enterprises Architectural Woodworks
These are the days of miracles and wonders, this is a long distance call...........
Why look here?
How do you build a box for a 2x4 wall?
I'm sorry, I thought you wanted it done the right way.
3/4" ply faces and a 2" rip of SPF..gives yoa a 3.5" header with 2" of pink foam..R10.
Spheramid Enterprises Architectural Woodworks
Adomition, beckons predition to the eyes of the soul...or What?
Why look here?
How do you attach this header box to the surrounding members? Do you first glue the spf to each plywood face? And do you nail the 3 layers together? Do you use a Simpson header hanger? I'm having trouble picturing toenailing the sides of the header into the king studs; is that how you do it? Also, the 3-layer header you describe seems to me more like a "sandwich" than a box. A box would have a top and bottom face as well. How many faces of plywood are there in your header: two or four?
HI..
How do you attach this header box to the surrounding members?
Either a Simpson or PL and toe nails ( at this point, keep reading)
Do you first glue the spf to each plywood face? And do you nail the 3 layers together?
Yup..sorta..glue applied to the "frame of the box of SPF and add isul..then the next skin of ply on both faces
A box would have a top and bottom face as well. How many faces of plywood are there in your header: two or four?
Ply is only on 2 faces..make a frame of solid stock to fit the hole, the skin the broadest faces with ply.
A 3/0 door would need a cut list like this: 2@ 41" 2x4,top an bottom, 2@ 8.25x 2x4.. vertacle legs, 2 (ply skins, @ 41"x 11 1/4"...) fill with insul ..
Need more help? Spheramid Enterprises Architectural Woodworks
I've been welding all day, what is YOUR excuse?
I get it; Thanks! By the way, what's PL mean?
LOL..not a clue!
It is a trade name for a polyuethane constuction adhesive..caulk type tubes..Lowe's ) if you have one) will have it.
If not , ANY good subfloor type adhesive ( NOT LIQUID NAILS) will suffice...OSI comes to mind....
Caught me off guard..LOL Spheramid Enterprises Architectural Woodworks
I've been welding all day, what is YOUR excuse?
Barbara,I may have this wrong, but I seem to recall that when PL 400 first came out, I think in the 1960's, it was "Plasticon," and the PL came from that. A short Google search failed to confirm this, however.Bill
Ed,
"For a normal door or window header, standard constructio is a doubled 2x with 1/2" ply in the middle"
We use 2-2x10's with a 2x4 on the bottom no plywood in between.Using plywood in between is not standard around here in NJ. I don't see any reason to use it and never see anyone using it. I did use it when I framed in Cape Cod 20 years ago but not here.
You're right; as others have said, it's for thickness only. We often used 1/2" Styrofoam if it was available on site.
I was talking to an engineer and he stated that plywood between two boards adds to the strength.
On another note, I was a site recently and saw the crew using I think its called "laminated veneer lumber" for the headers. I think it cost more but all they had to do it cut the board to the length of the header and they were done.
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So does cardboard. The question is, how much?
JLC had an article addressing this a few years back.
The jist of the art. was that w/ 4 ply plywood 2 plys are running with the grain going verticle so they contribute no strength from an enginnering standpoint.
and the strength from the other 2 (or 3, for 5 ply) is minimal.
If you need extra strength in the same thickness you need to go deeper(2x12 vs 2x10), switch to LVL, or add a steel flitch plate.
But most headers on windows less than 4 feet are over designed any way.
as always, check your code book for an appropriate span/sizing chart.
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This is a subject I've seen debated at length. I've never seen any solid evidence one way or another.
Personally, I doubt the ply does much good. Around here, it's often only some odd scraps thrown in - Not one piece all the way across.
If the ply was one continuous piece, and was fastened well, I could imagine it would add something.
But for the most part I think it's just a spacer.
The plywood is for packing. I nail the 2x's together, then nail a full size piece of plywood to the inside of the header. This prevents sheetrock cracking over the door and window heads. The lumber shrinks, the plywood doesn't.Have not had a call back for sheet rock repairs in 40 years.
mike
Mike, I like your idea!
I'm going to give it some thought.
blueJust because you can, doesn't mean you should!
Warning! Be cautious when taking any framing advice from me. There are some in here who think I'm a hackmeister...they might be right! Of course, they might be wrong too!