Hello,
I am framing a house with 16 inch overhangs. Usually we have 12″ overhangs and just use 2×6 blocking between the gable truss and the fly(barge) rafter.
This house I ordered a reduced gable truss(reduced 3 1/2″) and we end nailed 2×4 lookouts to the first common truss and cantelevered them over the gable truss to the 2×6 fly rafter. We put them every 2 feet. From what I’ve heard, read and figured, this is a very strong overhang.
My question is if the cantelever distance on one end is ok. Because of layout, the last common truss sits about 9 1/4″ (inside to inside) from the gable truss. So on the lookout I have about 10 3/4″ inside the building and 16″ cantelevering out including the fly rafter.
I’m wondering if this is sufficient? I realize everthing’s all tied together and 16″ isn’t all that much of an overhang. And I know for 12″ overhangs some guys don’t supply any reinforcement but I’d rather overkill and error on the strong side.
Any comments would be appreciated.
Thanks,
Booth42
Replies
Any reason you couldn't scoot that last truss over a bit? You generally keep them on 2' centers so you don't waste plywood, but it doesn't really matter on that last truss most of the time.
Even if you can't, you overhang is probably fine. Just make sure it's fastened well, and your building inspector is O.K. with it.
Truss Designer Extraordinaire
Sometimes it helps to look at what will have to happen first for a design to fail. In this instance the cantilevered lookouts will have to lift the sheating and detach or shift upward from their attachment to the last common truss. Given the leverage on the attachment point they probably could shift upward if attached by nails thru the truss into their endgrain. The sheating might be loosened also by the lookout being levered up under heavy live loads. I think that typical nailing might allow this overhang to sag over time. Combined with the consequent hump in the sheating on the first common rafter this could look ugly.
I think a 2x4 joist hanger used upside down on the lookout to truss attachment would be cheap insurance. On what centers had you planned your cantilevered lookouts? A switch from 32" centers to 24" for example would grealy increase the strength of the overhang. No doubt you already planned on carefull extra thourough nailing of the sheating near the overhang.
joe d
I agree. I usually attach hurricane clips from the gable rafter to the lookouts which I usually place 24" OC
I'd move the truss. 918 Contracting - Residential Construction
It sure wouldn't hurt to run your lookout blocking all the way into the second truss into the house, even just every second one.
For the extra twenty minutes work, it is cheap piece of mind.
How could you run the lookouts back to the second truss?
Joe D's suggestion of 2X4 hangers upside down was a good one.
Truss Designer Extraordinaire
You're right.
I was thinking of a full size rafter, not a truss web. You don't want to notch a truss like you would a rafter.
So, I guess I come down on the side of moving the truss.The good are lucky
Hi guys,the sliding the common back is the answer. Unfortunately, I wasn't bright enough to think of it ahead of time.The roof is all sheated already with 1/2" OSB so there's no movin' going to happen now.Also, I don't see how I can put joist hangers on after the fact either.It's a 7/12 and the lookouts are every two feet so I'm not too concerned. I just wish I had thought a little more first. We usually don't use lookouts on our overhangs.(usually don't do 16" overhangs).But when an architect designs a 29'x49' house you can bet he'll put wacky overhangs on also. The waste pile keeps on growing.How about sistering 2x6 blocks to ever other 2x4 and cutting them snug between the dropped gable and the fly?Thanks again.
Move the truss or increase the number of lookouts. I'd move the truss if at all possible, try to get 16" on the inside
Booth,
After snow loads and DL I always calculate what the stress is on a lookout is if a 200 lb guy is hanging on the end (because you will be). A #2 HemFir 2x4, 16" long (using a load duration factor of 133%) would be at 2438psi, about 96% of it's rating. Most lumber is much stronger than it's rating by about a factor of 3 so 16" is no problem. The Two 16D's that you fasten it to the common rafter aren't stressed too much either. No problem.
Darrell
Darrell,
thanks for the reply. Are your calculations based on 16" outside the building and only 9 3/4" inside the building? Just making sure. If they are, I take it the other end of the building with 16" outside and 24" inside must be strong enough to hold up a car. I notice a lot of guys put 2x4 lookouts flat and notch out the gable rafter. What's the strength gain by tipping that 2x4 on edge?
Booth
Booth, I did the calcs for 12". Sorry, I didn't notice the 9-3/4" you mentioned. The 2x4 would be held down by the sheathing as well as the end nails and it wouldn't hurt to install reverse hangers as the other guys mentioned. Up on end you gain about 2.33 x strength, but it may be better to just put them at 12" OC.
If its too late for a joist hanger then use an angle clip.