I am building a small outbuilding using 8/12 roof trusses over a twenty foot span. I plan to join the bottom of the barge to the extended 2x subfascia, but am uncertain of the best method to attach the blocking and the ridge. I’ve seen the blocking let in to the gable rafters on stick built construction but I am concerned that the 2×4 makeup of the rafters would be too small for this method. Can I conntect the two barge rafters at the ridge using a Simpson-style bracket? Thanks in advance.
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When you order your truss package specify a drop gable truss for each end. Normally the truss plant will automatically assume this is what is needed. Then you'll overframe that with 2x4 rafter extensions on edge, 2' OC, some call them "lookouts", tying them back to the first common and letting them hang over whatever. A 2' overhang is about all that is recommended for a 2x4. As you go up the rake you block between each.
I figure out what my sheathing pattern will be so that the lookouts fall on the ply joint.
"When you order your truss package specify a drop gable truss for each end. Normally the truss plant will automatically assume this is what is needed."
I don't like the word "asssume" when you're talking about trusses. I would suggest being VERY specific about how much you want the top chord dropped.
I've dropped top chords 1.5", 3.5", 5.5", and 7.25" depending on what the customer wanted in each case. So if someone asks me to drop a top chord I always ask how much. But other designers without much experience might not know to ask.
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I hope I'm reading this right. If you are concerned with weakening the trusses by letting in blocking on the gables, get your gable trusses built 1 1/2" or 3 1/2" shorter than the commons. It is a pretty standard thing for the truss guys to do.
Edit: Ralph beat me to it and explained it way better.
Edited 3/19/2007 11:42 pm ET by fingersandtoes
Here's a pic of what I'm working on now:
.View Image
Edited 3/19/2007 11:57 pm ET by RalphWicklund
How much overhang?
Have you already got the trusses?
What snow load requirement?
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If you cut into your gable end trusses you will likely have an inspection issue on your hands, not to mention that you are right in saying that it would significantly compromise the structural integrity of the upper chords.
Regarding ordering dropped gable trusses, yes that is done sometimes, but I wouldn't say it is assumed by any means. Further, it tends to be problematic in that for some reason the drop often doesn't comes out exactly right to where the lookout blocks don't need to be either shimmed or trimmed, or both. I've had this with several different truss companies.
If the trusses are already ordered with no dropped gable, and the total overhang is 12" or less, just sheath your gable end trusses and then nail the 16" O.C. lookout blocks to them. Then nail some Simpson strapping on top of the blocks tying them to the gable end truss framing. This is normally done before the gable end truss is craned in place. If you are not using a crane, often the sheathed gable end truss is put on top of the walls, the gable overhang is assembled, and then the gable end is stood up in place. BTW - as long as you are preassembling, nail the gable end deadwood in place before the gable end is installed.
"If you cut into your gable end trusses you will likely have an inspection issue on your hands..."
That definitely could be an issue if you have inspections. Getting approval first from the manufacturer should head off any problems.
"...it would significantly compromise the structural integrity of the upper chords."
I really doubt that's the case, assuming the gable studs are 2' O.C. or less, the gable is sitting on a bearing wall, and they're only notched 1.5" deep.
We actually notch gables in the shop and send them out that way when customers request it.
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Boss,
My understanding is that most gable end "trusses" are not really trusses to start with. Rather they are simply a flat framed gable wall assembled at a plant that also makes trusses. Here I have to order a true "Gable End truss " with infills for studding.
I have never had a problem with the notching , with the exception of a cantilieverd overhang.