Over Framing A Cross Gable Roof To A Open Great Room (cathedral)

 
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Old 09-01-2011, 01:53 AM   #1
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Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


I have what I hope is a fairly simple question.. I will be building my second home this fall if all goes well. My question is, can I sheath the entire roof of the cathedral roof.. 12/12 pitch, then frame up the other rafters for the cross gable 7/12.. then extend/continue off of the LVL ridge beam of the cross gable with a 2x12 conventional lumber over to osb sheathing on the cathedral roof, snap some chalk lines and frame in the valleys directly onto the the osb..I believe this is called over framing, but is it an excepted practice?. hoping to get away with all the additional framing of valleys beams and such to the cathedral I-joist rafters.. Some details of the design include a clean span LVL for the 44' great room with wood I joists for rafters down to the bearing walls of the great room.. also the cross gable will also have a LVL beam and also be constructed rafters with wood I joists..

Thank you for any replies
Kevin..
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Old 09-01-2011, 02:13 AM   #2
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


Are you talkin bout a cross gable or a dormer because a dormer is done one way but a cross gable is done completely differently is if you could include a pic of your drawing maybe we could give some more detailed help. Maybe your referring to a geometric perpendicular reticulated gable?

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Old 09-01-2011, 04:46 AM   #3
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


Depending on the codes in your area, but I've never heard of it not being allowed. Lay some valley sleepers down though. Don't put bearing jacks straight onto osb.
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Old 09-01-2011, 09:25 AM   #4
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


What DWB said, we need more information about your actual condition as the framing can get pretty complex...or not.

And for a visual about what Kent was talking about see below. The valley sleeper board distributes the roof loading from your over-framing across multiple rafters. Especially important in areas that have large snow loads. Also some areas require that 'attic spaces' be ventilated or filled solid with insulation AND if you are in a high fire zone, the local Fire Marshal may require fire proofing of and 'inaccessible space'. Of course I live in the Bay Area and people are a bit twitchy about our hillside fires...

Valley Sleepers


No valley sleepers

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Old 09-01-2011, 05:02 PM   #5
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


Than you. And yes I believe what I was hoping to do was an addition like the one in the pic you provided with no sleepers where it looks as though the valleys are framed directly to the osb. And no not looking for a dormer, just more living quarters on each end of the great room. But the roof line coming in at 90deg to the great room roof line.. I will attach a photo if I was can
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Old 09-01-2011, 05:44 PM   #6
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


if you overframe on a cathedral you just won't see the valleys or the shape of the intersecting gable from inside
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Old 09-01-2011, 05:59 PM   #7
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


That is correct.. and not an issue.. just wanted to know if this is excepted practice.. and will not cause a framing issue.. if I have to lay the valley sleepers directly onto the 11 7/8 wood I-joists to run the jacks down before I sheath just makes it more difficult to navigate around and then try to get. Sheathing under to close off the vaulted ceiling later is all..
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Old 09-01-2011, 06:02 PM   #8
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


Quote:
Originally Posted by rusticlife View Post
That is correct.. and not an issue.. just wanted to know if this is excepted practice.. and will not cause a framing issue.. if I have to lay the valley sleepers directly onto the 11 7/8 wood I-joists to run the jacks down before I sheath just makes it more difficult to navigate around and then try to get. Sheathing under to close off the vaulted ceiling later is all..
yea, overframing is fine usually
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Old 09-01-2011, 06:15 PM   #9
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


I've always called that a reverse gable. In any event, we've done many similar to the picture Fargo03 posted with a few exceptions. We put sleepers on the plywood first along the valley, then bear the rafters on the sleepers. This protects from a concentrated load being imposed directly on unsupported osb.

If the attic space on the existing building side is enclosed (the ceiling is not finished on the underside of the rafters, we cut an opening in the osb inside the area covered by the new roof to allow air movement between the two. This hole should also be large enough to provide the minimum access if needed.
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Old 09-01-2011, 07:20 PM   #10
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


the sleepers are not only for proper load distribution, but roof to roof connection and boundary nailing for roof ply
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Old 09-01-2011, 07:55 PM   #11
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


I don't think I would except it
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Old 09-01-2011, 10:50 PM   #12
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


Very common around here. Many framers call it "valley fill" or "overframing".

It's usually done with the plates described above at the perimeter of the valley, and with the ridge board and the longer valley rafters posted down at 48" centers to distributed the load more evenly across the lower roof.

It's also important to have sheathing on the rafters or trusses below (underneath the dormer) to prevent buckling of the rafters or top chords, which are usually in compression. Small access or ventilation holes in the sheathing can be cut if needed, but don't leave those framing members unbraced.

That LVL beam you speak of isn't spanning the 44 ft is it?

Framing with LVL and I-joist is wise for the main roof, but probably is wasting money on the overframing. I've seen some big valleys framed with 2x6's and 2x8's when it's supported on jacks posted down to the main roof.
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Old 09-01-2011, 11:15 PM   #13
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


Rusticlife,

Sorry for the small confusion...those pictures were to get a more clear understanding of your condition (and found quickly on the net this morn before work). The upper drawing is not how it should be done either. It is actually a combination of the two!

If I was your architect/engineer I would run the sheathing (OSB) of the main roof down to where you want to terminate that plane of the roof. Then install valley sleeper on top of the main roof sheathing, a 2x8-2x12 depending on the rafter size. As Parkers said the sleepers are not only for load distribution, but to act as a boundary nailer for the secondary gable. This will stiffen your roof and help tie it to the main roof as well as giving you something to perimeter nail the sheathing for the secondary gable (as well as a good base for your valley flashings!). The rafters in the overframed area need not be the same size as your main rafters (assuming you are doing a cold roof and/or cathedral batt insulation). But if you are venting the roof (I highly recommend it even if it is not locally code required) then you will also need to drill some holes in the main roof sheathing under the over-framing to allow for ventilation. This gets a bit complicated if fire code comes into play....

Hope that helps a little.
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Old 09-02-2011, 11:59 AM   #14
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


Here a lay on we just did this morning !
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Over Framing a cross gable roof to a open great room (cathedral)-image-3516497246.jpg   Over Framing a cross gable roof to a open great room (cathedral)-image-3975052816.jpg  
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Old 09-02-2011, 12:15 PM   #15
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


Where was that picture when I was googling? Nice clean work there FramerPDX.
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Old 09-02-2011, 07:14 PM   #16
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


thanks bro ...
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Old 09-06-2011, 08:11 PM   #17
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


Framer pdx.
thanks for the great pic and info, I now believe I wont have an issue with the over framing. Now I will try and figure out how to ventilate that space.. seeing as I was planning on a hot roof with closed cell spray foam for the vaulted area...

Thanks again
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Old 09-22-2011, 03:53 PM   #18
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


Size of the catherdral structural ridge and size and span of the rafters would determine what kind of overlay load is acceptable, you should probably put cathedral rafters at 12" o.c.if they are a longer span rafter. i would always put down sleepers to distribute the overlay load.

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Old 09-22-2011, 04:12 PM   #19
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


I know this is a how to question, but can anyone tell me how to upload pictures on this thing. thanks,just another no it all newbie.
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Old 09-23-2011, 11:39 AM   #20
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Re: Over Framing A Cross Gable Roof To A Open Great Room (cathedral)


We do what your asking quite often where I work, usually using 2x6 rafters and 2x10 sleepers. The sleepers are the way to go, you can easily spike them into the existing rafters through the osb. its a hell of alot stronger.

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