Constructing a beam from 2x10 's

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I've read a number of articles on this. One method said to use 1/2" PT plywood 10" wide triangular shims every 24 inches to prevent water from getting between the beams, and to let it dry out by the PT Plywood.
This seems odd to me since this would tend to weaken the beam? Does anyone really do this? ALso I would thin kPT Plywood would be a lot less durable than 2x10 PT? Is it really practical?
Also, let's say my header is 12' long. What carriage bolt spacing should I use? I was thinking 24", staggered on-on-top, one-on-bottom?
Thanks! BX1
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It would help to know what you're building a beam for. Unless this beam is exposed to the elements, I would not use PT at all. Also - where was it suggested to you to use carriage bolts on your beam? For normal applications, simply nailing the beam up with 12's or 16's is more than sufficient. There's overkill, and then there's overkill...
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I agree that if it is not exposed to the weather (or touching the ground since we don't know what you are spanning with this beam) I wouldn't use pt lumber or plywood. Real overkill would be to sandwich 1/4", 3/8" or even 1/2" steel plate between the 2X's and bolt it all together. I only mention this much overkill because the only time I can think of using bolts with beams was in a past life as a framing carpenter. We framed out a grand entry way that had curved oak staircases rising on both sides of the entry and we built beams like this as the header(?) at the top of each staircase tied into a manufactured exposed beam between stair headers. Robert Smith Jacksonville, Fl.
Mike Marlow wrote:

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So I'm slow. I guess I should have finished reading the thread before putting in my 2 cents worth. You guys got to this all by yourselves. I'm not used to being around people that think on their own. But flitch plate? Is that a real word? Robert Smith Jacksonville, Fl.
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Knotbob wrote:

Yeppers, it surely is.
Flitch... 3. a beam formed of a steel plate between two beams bolted together: in full. Flitch Beam...
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You are talking about engineering details that could mean the difference between life, and well, not good things
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On 28 Apr 2005 05:05:51 -0700, the inscrutable "Buell Boy"

I'd talk to several beam manufacturers to find one in my price range rather than risk faulty engineering data on my or someone else's life. Glu-lam type beams might even be cheaper than doing it yourself.
Look around for overages or cancellations from local builders, etc.
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Which is it a header or a beam? A header spans the space over a door or window. Which I suppose is a type of beam. Generally you need 1" of header for every foot of span. Therefore a a 12' header should be constructed of 2x12 lumber, not the 2x10 you suggested.
For beams.... all bets are off. it depends on what you are supporting.
Please do not take offense, but the fact that your question is poorly formed suggests that you are a bit in over your head. You should speak to a pro (Engineer or experienced framer)
-Steve
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Is this supposd to be an exterior beam? If so flash the top and forget about the shims. If it is not exposed to weather forget about the shims. If the 2x10s are placed side by side (oriented vertically) then it hardly matters at all whether they are attached to each other. If they are properly blocked to prevent rotation and buckling the there is no force that is acting to push them apart. Nails should be fine to hold them together. I think that the UBC has some information about required nailing. Check that out.
-j
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on 4/28/2005 11:50 AM J said the following:

Correct but he's referring to a BEAM which, in most parts of the country, is considered to be a horizontal cross member which supports a load. He further indicates this by referring to it as a 12' HEADER. You're speaking of a post or piling<g>
I constructed a header for a 16' overhead door opening on the garage I built. The sidewall containing the open was load-bearing for a truss roof. I laminated a " ~17'x9" steel flitch plate between the 2x10's and bolted the whole thing together with carriage bolts as he proposes (staggered). The garage is now 20 years old and there is absolutely NO sag in that header - none. It'll take a fire to make that puppy sag. Overbuilt? I dunno. That's what the plans called for in the header.
IIRC correctly the " steel flitch plate w/bolts may have been an alternative to either " or 3/4" ply nailed.
BX1's best bet is to check with Building/Zoning or Community Development in his town and see what they say. To overbuild is never a crime<g>
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news:BH9ce.944> > Is this<snip>

I'm working on a garage design. For a span greater than 9 feet, our local code requires two 2x12s sandwiched around a 1/8" steel flitch plate. I'm curious where one would obtain a 17-18' long steel plate 11.25" wide.
todd
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From a steel fabricator?
You sure they wouldn't accept a glue-lam or LVL beam?
-J
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on 4/28/2005 2:45 PM J said the following:

Exactly, and it's my bad on my earlier post, it IS a 2x12 with the flitch plate and it's still not going anywhere.
Ordered up the flitch plate from local steel dealer that supplies the I-beams, etc. and gave them the dimensions. Brought it in, dropped it off the flatbed. Had a small table top drill press and set up a little staging area about six or eight inches off the ground and drilled the holes to spec.
I must have been crazy to do it but I hoisted all three components up into position by myself using a fence comealong, chains and temporary supports. I was quite proud of having done it by myself. SWMBO thought I was crazy. Now, I would tend to agree<g>
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That's old tech...glue lams have long ago replaced that method. Look up I-joists, glue-lams, or LVL.
The old 2 2x12 method will work, but there are much better methods for headers.
http://www.i-joist.org/home.asp
http://www.ufpi.com/product/lvl /
http://www.curtislumber.ca/products/gluelams.htm
Todd Fatheree wrote:

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Todd Fatheree wrote:

With today's engineered beams, the above sounds like very old technology to me.
Think I'd do a little more research.
Lew
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Well, I broke down and gave the building department a call. Though not called out in the spec sheet, they will accept an LVL or gluelam header.
todd
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I am too. By vertically I mean that the beam is 9 1/4" deep with the 2x side by side instead of stacked (which would be a bad idea).

Actually I DID write about a beam. With a post, bonding the two (or more) together is MORE necessary to prevent buckling.

A 17' load bearing span is definitely too much for a couple of 2x10's. In your application, the steel is doing most of the work and the wood is there to keep it from buckling (also to nail to I presume). I'd hardly consider that to be overbuilt.

Without knowing the loads, it is hard to say, but it is quite unlikely that you could have substituted a 9" wide piece of 1/2" plywood for the steel. Making the beam deeper (perhaps using the plywood as a web) would certainly help. Beam deflection decreases with the cube of the beam depth.

Good advice. This is really a simple case and they should be able to give him an answer based on codes.

Actually I consider it equivalent to theft if I am the one paying for it. If not, then it is simply good practice.
-j
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Overbuilt can cause a failure. For example, if something is designed and built correctly, it will tend to show excessive deflections before failure, providing a warning. Overbuilt things can fail spectacularly without any warning. That could be a crime or at least expose you to a civil lawsuit.
Mike
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wrote:

Um, I'm not so sure about this. In fact I'm trying to remember if I've ever seen that happen. Do you have any specific cases?
I'd venture that things fail more often by being underbuilt, OR not being built to plan. Such failures are commonplace.
Overbuilding is not particularly dangerous, but it is wasteful.
-j
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Uhhh .... howzat again? Seems to me that if it fails, then by definition it was underbuilt, not over....
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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