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I’m working on my first hip roof with trusses, and a few questions came up to me before I’ve started the job.
* Is a PT sill (CCA 0.33) appropriate for permanent contact with concrete?
* Is there a need to add hips between the trusses (4/12), knowing that the sheating is a 3/4″ T&G fir, and that the snow loads are very low due to the geographics position (atlantic region maritimes) ?
* Knowing that the trusses are 2ft oc on the ceiling side, of course with the pitch the on center spacing is now more than 2ft. Have you got a tip for this one?
Replies
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P.T. is fine for perminent contact with concrete.
There is no need for adding the hips in between the trusses
although I just about always do it. I also run blocking up the roof from the jacks to the hips and keep the sheathing running perpendicular to the rafters. I've been told a number of times that this is overkill and that I should just run the sheathing parallel to the jacks. Try sliding this one by a building inspector on a conventionally framed roof!
All thing considered I like to frame hip roofs with, and most all roofs for that matter, with conventional lumber.
*I'm a little confused about whgat's going on with your hip system. What kind of span are we talking about ? How far is the hip girder from the end of the building ? We always try to use as long a setback as we can to try to minimize the need for blocking. But the way hip roofs are framed varied a great deal from region to region.One thing that might be helpful is a "hip gable". It's a gable that's built to sit on top of stepped-down trusses, and eliminates the need for blocking. Some truss companies do this, and some don't. Another option that comes to mind is that the truss company can simply drop the flat tops of the trusses by the thickness of a 2X4 laid flat. (Similar to the hip gable thing) Then you lay 2X4s in parallel to the hip jacks and nail your plywood to them. This is probably something your truss supplier deals with frequently. You might also try talking to them about it.
*I agree with kcoyner regarding the use of conventional lumber. Sometimes the size of the building and layout makes trusses more appealing. Here's what we do when trussing hips.Ask your truss manufacturer to drop all trusse by 1-1/2 inches from and including the girder up to the commons. This allows you to lay 2x material flat on top of these members in line with (parallel to) the jack or mono pitch trusses. This provides for two foot o.c. nailing for orienting the sheets in the proper direction. This is common in my area and speeds things up over installing blocking. Some manufacturers can even fab the nailers, similar to a truss, provided it is not prohibitively large. We also like to fab anything we can on the ground. You can find some articles on these techniques in back issues of fhb and some other trade mags.Always string your hips, best of luck.Tom
*I must agree here with Ron about dropping the flat tops and then running purlins of a sort. This is a way great way to make the truss system. I haven't seen the local truss companies design a system this way on any jobs I have worked on however. If I use trusses for a hip, it means someone else has done the ordering and the flats aren't droped. Also good advice to talk to the truss supplier.
*I've done the individual blocking, but lately (the last few years) the stepped down trusses are intentionally dropped to receive a layed on framework.Some truss companies provide that framework, but most do not. i've built many on the gorund and craned them up.I don't mind doing it any of the three ways. each has their plus and minus's.I always like some type of solid nailer at the hipm becuase we are normally using 7/16" osb.blue
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One little thing you'll run into with dropped hip truss packages is the 2x4 purlins (laid flat) that act as hips only provide a solid nailing surface on on side. I use short bevelled blocking, nailed to these purlins from truss to truss so I have a nailing edge for the sheets on both sides of the hip. Your truss company may provide some framing details.
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Here's what Ido for nailing on my dropped hip trusses.Rip a 2x6 1and1/2" to the short point of a 45 degree bevel for my hip purlin, this gives me the 1and1/2" on one side and about 2"on the other to staple the sheathing to. By the way don't measure the 1and1/2" just do a skinny table rip,also this gives you 2 hip purlins for each rip you make.When I nail it to the trusses I line up the long point of the bevel with the flat top of the truss,making sure the trusses are properly spaced.This way you can cut your common purlins into the hip purlis fairly easily. I like the idea of stringing you hips.
*Ran across this Jpeg image of a "hip gable" used on a hip roof. Thought it might be of interest. I don't know who took the picture, or where it came from.
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Dear Jim,
Thanks a lot for taking time to help me with my problems, I really appreciate.
Therefore, I've haven't really undestood the way you're dealing with these hips.
What's the difference with James Hawke suggestion (Nov 2/ N°6)?
I'll hope to read you soon Jim at great white.
Thanks!!
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Hey Phil,
Here's a crude drawing that may either clarify what I meant or possibly totally confuse you. The difference between my solution and James Hawkes, I think is really in the number of sticks you are going to cut.Please see attachment and good luck.
Jim, at Great White
P.S When you are done it should look like that photo from the reply prior to tis posting.
*Ron - how are the lower pieces tied back into the building? Are they only attatched to the hip girder and the top plate? That looked like gravity was gonna pull them down. Not so? Thanks - jb
*Jim - By "lower pieces", I assume you mean the hip jacks that go from the front wall up to the hip girder. They're triangular in shape, and have a bottom chord. The bottom chord rests on the exterior wall, and is mostly hidden in this particular picture by the subfascia. Is that what you mean ?
*Yeah, that's the one. That looks to me like the fascia would sag. Is there a diagonal web from the plate to the top chord that I can't see there? What keeps the facia from sagging? Thanks - jb
*Phil I was just thinking that with a 4/12 pitch that a 60 degree bevel on the 2x6 would probably work better.Everything else stays the same.
*Jim - Have another graphic for ya to look at. Maybe it will clear things up a bit. It's a "side view" of the hip jack. It goes from the end of the building back to the hip girder. Does it make any more sense now ?
*That looks great, thanks. I got the impression that the girder was right at the wall from the other pic and I couldn't figure that part out either. Man, I tell you, whenever someone starts describing a situation with words, I get lost. Nothing like a picture to clear things up. Thanks again. - jb
*Jim - Have another graphic for ya to look at. Maybe it will clear things up a bit. It's a "side view" of the hip jack. It goes from the end of the building back to the hip girder. Does it make any more sense now ?
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I'm working on my first hip roof with trusses, and a few questions came up to me before I've started the job.
* Is a PT sill (CCA 0.33) appropriate for permanent contact with concrete?
* Is there a need to add hips between the trusses (4/12), knowing that the sheating is a 3/4" T&G fir, and that the snow loads are very low due to the geographics position (atlantic region maritimes) ?
* Knowing that the trusses are 2ft oc on the ceiling side, of course with the pitch the on center spacing is now more than 2ft. Have you got a tip for this one?