20' Header Over Garage Door?

ASIinc.

Doing a 20' door on a pole building. Can I get away with double 2x12's or do I need LVL's. They will be sitting in notched 6x6 and attached to truss. The only load it will carry is itself and door track. If I attach to truss will it still sag and is it too much weight for truss to hold?

JonM

Call your lumber company and have them calculate an LVL for you...I suspect you have snowloads in Maryland also...

Brock

suggest stuctural engineer look at it.

bwalley

I doubt it, I would have to look it up.

An engineer should be sealing the plans and doing the load calculations.

What is the live load and dead load on the roof?

The trusses should be bottom bearing trusses and will not need any support other than the end walls, if they are sized and built correctly.

bighammer

is the door on the end or side of the building?

how wide is the building?

what are the truss loadings?

how far apart are your posts?

We set the gable truss and sometimes hang the track board off the bottom chord..depending on the door size and weight?

is the door a Tab-loc , meaning all steel, or is it a wood framed unit?

ASIinc.

-door is on gable end
-24'
-dont know but they are 2' O.C
-20' apart
- Door is gonna be steel.

Basically the truss would be keeping the 2xs from sagging and holding the track. Should the roof load really affect that beam?

Brock

Legally I feel it's best that I step away from any more advice at this point.

Good luck

72chevy4x4

go to the truss designer and ask their engineer to tell you-shouldn't cost you anything. They may suggest doubling up the trusses at the gable end in order to hand the header. The point load of the door should be within 2' of each outside wall-you're putting another 6x6 posts there, right? You may find a 16" lvl will do the trick-but unless the 2x12 it fastened to the bottom chord of the truss throughout it's length, I wouldn't trust it 5 years down the road.

bwalley

The Truss will put a little bit of weight on it but not a whole lot, the majority of the weight will be split evenly by the two side walls, the truss company will size the trusses, I would use a dropped truss for the gable end, it will make framing easier and stronger than building a barge.

I don't think you can span 20' with a 2x12 flitch beam, possibly adding steel instead of plywood in the middle would help, what you are concerned with is deflection on the 20' beam, deflection is the technical term for sagging.

The beam does not carry the weight of the door, it supports itself and the tracks bolt to the sidewall of the post supporting the flitch beam.

Your Engineer should figure all of this when he seals the plans.

ASIinc.

Yea Im just concerned about sagging and I know most of the support needs to be towards the ends. The building is already framed and dried in. Im adding 2 more posts to give me my 20' rough. My plan was to span the 20' with a 2x12 beam that is attached to the bottom chord of the gable truss. Im just wondering if the truss can support this or will it end up sagging too much? This is my main question. The track Im talking about is the middle top track sorry Im not overhead door savvy.

bwalley

Trusses are not typically designed to support a load underneath the bottom cord, you may get away with it, but why take the chance?

If you were going to suspend a beam off of the bottom chord you should use a girder truss, but since it is dried in, you would have to tear off part of the sheating to install another truss.

20' is a long span for a 2x12, you could have your engineer see if using 20' of plate steel instead of 1/2" plywood in the flitch beam will help with deflection.

I would look into adding steel or using a LVL.

KennMacMoragh

I remember doing one garage door where I had nothing but a gable truss on top of it. You're right, there's no load over it, so the beam only has to support itself. I remember the beam we used was fairly small, you might look at it and think it's not enough. But when you think how the truss isn't putting any weight on it, it's fine. Of course it was still designed and approved, are you designing this yourself? I'd imagine that two 2x12's at 20' would be enough to support itself.

bwalley

I can't locate my SYP Span tables, a 2x12 flitch made of Machine Stress Rated Lumber may work.

You should have an engineer check the span instead of asking people on the internet.

cleveman

I imagine you're talking about 2x6 trusses on a pole building?

First of all, forget the engineer. That will take all the fun out of this.

Just figure out what the header and the door will weigh, lets say 400 pounds.

If the span is say 36', attach a long piece of angle iron to the bottom chord of the truss, say a 20' piece, or as long as you can find. Try to get something that will span from cross web to cross web. Make it 3/16 or 1/4 x 6 or '' wide. Install the angle pointing out, and drill holes in it to screw through and into the header.

Now put a ladder under the middle and stack some stuff on it until it is about an inch below the bottom chord. Find some lard ass or two and rig up a swing and get them to sit in the swing. Measure how far the bottom chord is deflected.

Report back with photographs for more consultation/condolences.

shanekw1

If only you could have seen how intensely I was reading this waiting to see what your angle iron contraption was going to do

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JumboJack

I did a garage with a BR above once.It was a long span,I don't remember how far.The plans called for a gluelam with a 1" camber.What a pain that was.It did'nt sag though.

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in texas with framing and cornish people will do it for 3.00 a foot. What do yall think about that? Just laber

bighammer

The posts are 20' centers, but the trusses are 2' centers, what kind of beam do you have to support the span? I've never heard of a wood structure with spans like that...anyway...

Trusses will have end bearing they are designed to clear span the width of the building....

I have built numerous post to truss buildings. The overhead door that size will require atleast 24" of head room for the track to make its curve. This is a simple question, the load of the trusses are on the sides of the bulding not the ends. This is why we use trusses, right, to clear span openings? Every other truss will support itself, this gable end is not any different.

You could get by using 2"x12" if you wanted, there should be very....very little load on this header....Post-to-Truss buildings are very simple, they should not require a engineer to stamp the plans. With longer spans like that, I sometimes will use engineered lumber or will splice my header, they don't make long sticks of lumber like they used too.

ASIinc.

Im not getting an engineer involved b/c this is a budget build for my wifes aunt. The plan was 2 9' doors but she changed her mind in favor of a 20'. Im trying to do it as economically as possible. I think everyone is thinking too far into this. I just wanted suggestions. If its too much PITA then she gets 2 9's. The truss wont be taking the entire weight rather just sorted helping it stay suspended. thats why I figured 2x12 would be lighter than lvl.

bwalley

a 2"x6" Flitch beam CAN not be used to span 20' (it will have too much defelcetion), look at the span charts on SYP or call an engineer.

An engineer needs to review and seal plans for any structural work, just for reasons like the bad information you are giving.

bwalley

An engineer will take about 10 minutes maximum to look it up, it shouldn't be more than $150.

Don't you need a set of sealed plans for a permit?

The truss has nothing to do with the 20' header, you need to understand how these things work and realize what you are doing by making changes in the field.

If you have a set of plans and are making changes don't you have to rvise the drawing and get the revisions sealed by a P.E.?

Why not just go to an 18' wide door? a 2"x12" flitch beam will span 18' with no problem.