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Old 04-14-2010, 08:08 PM   #1
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unsupported ridge beam


Just bought a cabin that was started but never finished, and has been sitting empty for 10+ years. There are some interior walls, but I plan on taking them all down and reconfiguring the way I want. Have a couple of questions that need answering. Cabin is 24 by 32, it has a single 2x12 for the ridge beam. Beam is in two section 20 and 12ft. There is no support directly under this beam, at either end or where the two piece butt together. Surely this should be supported down to the bottom plate, shouldn't it?

Second issue I have is that part of the cabin has 2x8 for rafters, the other part has 2x6. Both are on 2ft centers. The 2x8 section was going to be vaulted, the 2x6 not. There is some additional supports between the rafters and a wall in the middle of the room on the 2x6 section (but not on all rafters). Goal is to make it the entire thing vaulted. Is 2x6 stong enough to handle this? Should I sister a 2x8 next to it (would also make level aross ceiling)

pictures are of the two ends, which I was able to take before camera battery gave out.

Anyone's thought on this?
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Old 04-14-2010, 09:04 PM   #2
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unsupported ridge beam


hopefully the 2 x 8's are going across the 24 ft width.

even with 2 x 8 rafters, you won't be getting much insulation in there. not with an air space above it.

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Old 04-14-2010, 09:27 PM   #3
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unsupported ridge beam


More pictures would help. But as for as a ridge beam you really don't need any beam at all. The force from the two adjoining rafters will hold each other up.
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Old 04-14-2010, 09:37 PM   #4
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unsupported ridge beam


Most ridge "boards" or "plates" are only supported by the inward thrust of the roof rafters. This kind of system also creates outward thrust at the bottom of the rafters where they sit on the walls. The ceiling joists or ceiling ties connect the top of one wall to another and prevent the walls from pushing out and away from each other.

If you want to remove the ceiling joists to create a vaulted ceiling, you will have to replace the 2x12 ridge board with a true, massive ridge beam, that carries half the roof load and is supported by sound posts and footings each end.

Also, as mentioned above, insulating and venting (or not venting) a vaulted ceiling is more involved and usually more expensive than a non-conditioned attic.
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Old 04-14-2010, 09:49 PM   #5
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unsupported ridge beam


Agreed - what you have is a ridge board, not a beam
In order to have a ridge board instead of a beam you generally need to have rafter ties to keep the walls from spreading out

If you don't have rafter ties (doesn't look like it) then you have a problem
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Old 04-14-2010, 10:28 PM   #6
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unsupported ridge beam


Scuba, you are probably referring to collar ties rather than rafter ties. The floor joists (or ceiling joists, depending on your perspective) are the rafter ties for a building such as this, however in the photos you can't tell if there are floor joists, except the OPS said there were, so I assume they are present.

There do not appear to be collar ties, which would only be there to balance uplift forces from one side of the roof to the other during high wind events. Granted, collar ties are important, but scarcely critical, and can always be added later. Floor joists acting as rafter ties are critical.
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Old 04-14-2010, 10:54 PM   #7
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unsupported ridge beam


I see ceiling joists/rafter ties in the 2nd picture
I don't see anything in the 1st picture, which covers a large area
And the 2nd pic has some really weird 2x's at the top
Maybe supporting a roof overhang ?
Also looks like 2' spacing on the gable ends for studs on the upper part of the gable wall..with OSB ?
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Old 04-15-2010, 12:00 AM   #8
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The framing is of good quality. Gable studs 24"o.c. with OSB sheathing. The cathedral ceiling 2x8's at the gable need fire-blocking as they used a 2x4 for that nailer which allows a path from the vertical studs to the sloping rafter bay. The framing 2x4's flat to the roof sheathing are a standard way of framing the over-hang roof, nailed with a fly rafter or gable rake and barge board. The real plywood for roof sheathing and ply clips at joints between rafters is quality. I presume the 2x8's are also stamped #1 (with small knots), as the ceiling joists. If so, the span of 12' without a snow load would work for both. The problem is getting the required insulation in the rafter space unless using rigid foam board $, AND the non-structural ridge for a cathedral ceiling.

http://books.google.com/books?id=E5S...raming&f=false


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Old 04-15-2010, 09:09 AM   #9
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unsupported ridge beam


attached are two drawings of what I have currently, and what I want to do. I want to reduce the size of the bathroom and move, making the kitchen and living room area larger. Would be moving the doors for the bedrooms as well. The area above the bathroom and bedrooms can be left as is - ie 2x6 rafters with ties. So I guess the question remains as to how to support the area over the living room/kitchen. Would adding two 2x8 or 2x10s to the existing ridge plate, and supporting down to the foundation be adequate? It would be just under 20ft from the left wall to the intersection of bedroom walls.

thanks.
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File Type: pdf old.pdf (38.6 KB, 141 views)
File Type: pdf new.pdf (44.9 KB, 137 views)
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Old 04-15-2010, 06:41 PM   #10
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I suggest hiring a Structural Engineer to give you a solution and take full liability. He/she would give you size, material, fasteners, footings, posts, and diagonal shear flow for the new beam. Your Insurance Company will want a paper trail for coverage if anything ever goes wrong.....

Be safe, Gary
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Old 04-15-2010, 09:00 PM   #11
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What would one expect to pay for something like this?
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Old 04-16-2010, 05:23 PM   #12
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after thinking about this and researching more, I am considering forgoing the vaulted ceiling. Instead, thinking of installing ceiling ties(?) about 1 ft above top plate of side walls. Which would require about a 22-23ft 2x6/8. This should tie walls togethor, allow for easier insulation, and would still give an open/larger feel to the room.

The local big box store's flyer says 2x6s this legnth are available via special order (#2 grade or better) or could opt for 2x8 engineered lumber. I don't plan on using this for storage, so it would only be holding insulation and sheetrock.

Anyone see anything wrong with this? If not, would 2x6s be ok, or opt for 2x8?

thanks.
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Old 04-16-2010, 05:27 PM   #13
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I did similar to what you are saying

Instead of a vaulted ceiling I bought 12' & put those up on one ceiling - 8' high

Another ceiling I put up 12' rafter ties - ceiling is 9' high (7' walls)
Rafter ties need to be in the bottom 1/3 (I think) of the rafter
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Old 04-16-2010, 10:06 PM   #14
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IRC max. span ceiling joists: 2x6 at 24"o.c. = 10'6" 2x8 = 13'3" 2x10 = 16'3" I suggest you ask the local Inspector as he may accept 2x12"s at 24"o.c., depending on the species, the grade, the final span and the attachment to the rafters: http://www.engineersedge.com/civil_e...onnections.htm Install in bottom 1/3', Dave got that part correct in his post: http://myconco.com/ComEngProb.html

Be safe, Gary
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Old 04-17-2010, 07:05 AM   #15
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Originally Posted by GBR in WA View Post
I suggest hiring a Structural Engineer to give you a solution and take full liability. He/she would give you size, material, fasteners, footings, posts, and diagonal shear flow for the new beam. Your Insurance Company will want a paper trail for coverage if anything ever goes wrong.....

Be safe, Gary

I do this all the time for clients and contractors in my area. If you had called me to do this design check, I would provide a lump sum proposal, and it would probably be a couple hundred dollars. You'd get the calculations and a couple 8.5x11 sheets of drawings of the connection details and member sizes, plenty to DIY it and cover permit requirements. Full blown drawings would be extra.

For any future readers of this post, if you have a similar situation, don't be afraid to call a local engineer.

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