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Old 10-16-2009, 10:54 PM   #1
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Gable Roof Trusses Not Same Height


Hello all,
I have run into a problem that I just cant figure out. I built trusses for a 12x12 building and the pitch is 10/12 (39.8 deg) . Once I had all the trusses in place and centered correctly, there is a varience on the height ranging from 1inch to 3 1/2 inches. I do not have them cut to a birdsmouth rather they are currently sitting in strongman hurricane ties on the top plate tacked in currently.

My question is how do I resolve this issue without taking all of the trusses down? If I cut the birdsmouth at the same distance from the inside angle to the top plate on all trusses would this solve the problem or do I just cut the couple that are really way over and have a different cut on each? I am totally lost and cant seem to figure where I am running into an issue. BTW, the walls and top plate are all square and same height to within a nats hair.

Any help would we greatly appreciated.

Truss measurements from top of gable to floor and front to back:

162
164
163
162.5
165
165.5
162.5

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Old 10-16-2009, 11:19 PM   #2
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Gable Roof Trusses Not Same Height


1. I presume you are talking about rafters with a birdsmouth cut to sit on the wall top plate?
2. Did you trace all the rafters from a pattern rafter?
3. Do you have a ridge board and is it installed level with a string line, and straight?
4. Did you string line the walls for straight?
5. They have to have a birdsmouth level cut for 1-1/2" minimum bearing per code.
Be safe, Gary

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Old 10-16-2009, 11:32 PM   #3
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Gable Roof Trusses Not Same Height


1. Yes I am
2. I didnt trace them but I made all the cuts for the 2 beams all at the same time and the chords as well.
3. I do not have a ridge board, (seems now that would have been much easier)
4. Walls are nearly perfectly straight each one is off about 1 or 2 sixteenths

Does that help?
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Old 10-16-2009, 11:32 PM   #4
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Gable Roof Trusses Not Same Height


I don't fully comprehend all of your description, perhaps laziness on my part, but I've fixed plenty of messed up roofs. Fortunately yours is small. Plumb, square, and straight walls make for easily framed [near] perfect roofs.
You didn't use a jig to set up your trusses, then? If you pre-built all of them and they don't line up, then either you have cut them to different lengths, assembled them differently, or the walls aren't straight somehow. The measurement you need to get is from the top-plate to the center of your ridge line. It's likely different from truss to truss given your details. You can find the shortest one, then make all the others the same length as that one, but it's a difficult thing to do, especially if you're not very skilled (pro level) with a circular saw and ladders. Your pitch isn't the same on each truss if they are different lengths and they all hit the wall evenly on each end, so in my opinion you'd be better off taking them down and re-cutting them on the ground. Each top chord of each truss should measure exactly the same length from wall to ridge-line, unless there's a problem with the walls.

The next way is lazy and garbage, but it could get you by if you're not a perfectionist. You could cut shims from the tails to the ridge-line of each rafter to bring it up even with the highest truss. I've had to do this to fix roofs that I didn't frame and I didn't have material to cut new rafters for. Also for trusses that come from the factory all jacked up. Or... you could sister 2x's beside your trusses to bring you up even with your others.

IMO, the best thing to do would be to make sure you have the correct rafter length, which when transferred to your board is measured along the top edge, from long point that abuts the ridge-line to a point directly plumb from the outside edge of your wall. Check this versus your actual trusses you have already, if you can get them to work, fine, then cut'em up. If not, then cut them all to match the shortest one.
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Old 10-16-2009, 11:43 PM   #5
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Gable Roof Trusses Not Same Height


I was actually thinking about the point of sistering the ones with the issues and also shimming up, but I know that would probably look like you know what from the inside. I agree with finding the measurement from the inside of the peak to the top plate. Could I then just cut a birdsmouth there and adjust each one accordingly?

The thing that sucks is that I have all of the already up. I will note that as anytime you are dealing with lumber that the boards were not completely straight and also some of the boards were a bit longer than others but i really didnt think that would matter since I was going pop a line and put a straight cut on them for the fascia.

I made sure though that the angle was correct on each of them
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Old 10-16-2009, 11:44 PM   #6
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Gable Roof Trusses Not Same Height


You said you had no birdsmouth, I thought you were referring to the Simpson Strong-Tie VPA25, which is a variable pitch connector used to do what you are talking about... I'm all confused.


Anyway, there is one component of the mix that isn't right. Your trusses aren't identical or your walls aren't plumb, square, and straight. You can work around square to a certain extent, and straight within a reasonable amount, but having 3" difference in height isn't within reason, eh?

When I build "trusses" for smaller sections of larger roofs, for example... it's usually for just the very ends of the roof. I generally nail opposing conventionally cut rafters to the ceiling joist and nail a collar tie just below where the ridge will sit, then install a ridge. Then I fill the area between.
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Old 10-16-2009, 11:57 PM   #7
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Gable Roof Trusses Not Same Height


I agree after all I may just redo those trusses and build them on an identical template, then I should have no worries. I built them on 2x6 on 24 oc. Would you think that 2x4 on the same 24 oc would suffice as well on a building this size ? If so I may just scrap the others and go with 2x4s. I can use those 2x6s on some other things after I dismantle them later.
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Old 10-17-2009, 11:58 PM   #8
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Gable Roof Trusses Not Same Height


Took down the trusses today and the chord was the problem. Although I didnt think when I nailed them that it pushed out one side or the other, it did. Resolved the problem by getting the master truss on bottom and then I tacked the subsequent ones on top and then applied the chord and everything worked fine.

Thanks for your help

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