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I plan on talking with an architect soon, but wanted feedback from this community too. Please see the attached photo. I'm in Raleigh, NC and am using information from this site (http://www.totalconstructionhelp.com/joists.html) to make the assumptions that the beams used below would work.

My goal would be to have only the center wall being a load bearing interior wall. The biggest question mark I have is the beams which are 3 2x12's with 1/2" play between them to hang the 2x8x16s from. I think the others according to the table should have no problem supporting the ceiling.

Ceiling joist plan

So I think I might update it to the following structure. I've not really researched a whole lot, but it seems logical. Here is the new plan. The change is on the left using a similar beam structure as on the right with 12' 2x8's spaced 16"o.c. This takes the middle joists to be a little closer than 24"o.c. I also have the framing for the attic stairs and a vaulted ceiling in the bathroom. What do you think?

enter image description here

And finally here is the roof structure. It is a hip roof with a gable on the front. I had two contractors say that the roof is supporting itself and other than ceiling joists tying the walls together the roof has no other supports to the ceiling or walls in the house.

enter image description here

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I would like to use some of it for storage. I'm thinking the area in the front with all the extra walls would be where I'd lay some decking for storage. –  michael Feb 9 at 23:09
    
What does your roof look like? Where's your blocking and bridging? –  Edwin Feb 9 at 23:44
    
What you have is an excellent start, including the plan for storage too. The roof structure will be a factor too. It looks like there will be 2 peaked roofs, one perpendicular to the other. If that is the notion, and the roof rafters properly sized, all will work well. given the spans are good for the 2X8 ceiling joists too. I presume that has all been researched before you drew it. –  Jack Feb 10 at 3:30
    
I just realized you will need strap ties across the beam that is on the left side of the drawing. they can be placed over or under the beam, but they need to tie together the joists that are on either side. That way when the loading of the roof occurs and the joists are put in tension, they will not separate, causing the roof to sag. Since the attic will have no storage there you can reduce the height of the beam and run the strap ties across the tops. With the joist @ 24" OC even SPF will span 13'-3" with #2 with limited storage, then you could use plywood to tie the joists together. –  Jack Feb 10 at 12:39
    
@Edwin I added a pic of the roof structure. I'm not sure about the bridging. –  michael Feb 10 at 16:50

2 Answers 2

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The roof framing really helped. Since according to the code book, you can have limited storage in the attic with the framing you specified, I would still tie all the framing with a layer of subfloor, which in turn can be used as storage. This is because the hips will exert an outward force to the outside bearing walls. There may not be a real issue with this since everything is tied back to a triple beam and tied to an interior wall as well. I would still run plywood in the attic anyway. It will make a great work surface while framing the roof too. This will mean the beams will need to be made of 2X8s or LVL's, this is engineered lumber that measures 1 3/4"X7 1/4"X any length you need. IMHO, the 2X12 beams are way much bigger than they need to be. There simply is not that much live load for them to carry. The wall that is under the ends of the joists that are near this beam can have a beam under it, to help carry what little load (stored items) it may need to support.

You may want to consider adding a beam at the other areas where the rafters will cross over the ceiling joists, so that short joists can be tied to the rafters like the rest of the house. Another alternative is running the beam at the ceiling level the same as the hip rafters. LVLs will help here too. This would eliminate the long one that goes all the way across.

The only 2 issues that I see is where the vaulted ceiling will be and the access. The possible plywood floor may eliminate the need for the joists to tie through. The other is the lack of collar ties. they in essence help break the span of the rafters, since one rafter when loaded will try to push against the other, but the other is trying to do the same. Purlins with knee braces may do the same also, but they will bear on the ceiling joists, may not be a good idea.

That I know of bridging is not required in ceiling framing, although it could be added. A final note on the access and vaulted ceiling, the code used to require ceiling joists at 32" OC (joists on every other rafter) for conventional framed roof as a minimum. With the engineers blessing he may allow the openings with the plywood deck around it to pass.

A little over sight on my part. There will be room needed for the insulation, so the plywood deck will need to be high enough, depending on your climate zone to get anywhere from R-30 to R-49 to be run under it without compressing it. So, 2X12 beams will work with an overbuild the get the 2X8s to the same height with 2X4s that won't work nowhere else, crooked, twisted, cut too short, what have you.

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I think the 2x8's are probably fine as well. Any real advantage between LVL vs. 2x8s? I was wondering about the outward pressure of the hip. It's like no matter how I frame it there is no way to tie them across the structure. So I guess decking as you mentioned or maybe just some 2x4 stringers (not sure if thats the right term) between beams.. I'll see what the structural engineer has to say. Starting the project in the next few days. Thanks for the help. –  michael Feb 11 at 1:38
    
Much stronger material to use over spans. The manufacturers of this type of material have their own in-house engineers that will calculate what is needed for any given situation. I have used them before it is a free service and the building inspectors honor their results. The engineers will send the info by fax or email. –  Jack Feb 11 at 1:43

The first thing i notice is that there is no means of egress on the exerior walls, therefore you may be missing a number of load points that may be required in your design. The aforementioned bridging are mitre cut two by two's c placed vertically between the joists to prevent deflection of the joists and help prevent drywall cracksl The areas of concern here are the bedrooms,kitchen and living room. Good call on the strapping jack. I would personally install one by three strapping on the underside of the joists throughout the house and shim them for a better drywall finish. The addition of joist hangers at the beams should also help any separation issues with roof loads, snow loads and live loads. The rafter design sounds a little scary considering it snows down there. I hope you plan on erecting walls in the attic/storage area. Aside from these issues it's a nice design.

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Thanks, the strapping I was referring to was the metal type, it takes little to no room, so extra shimming would not be needed. They are sold prepunched for nailing, and can measure about an 1 1/14" wide by 5 or 7 or up to 18" long or it can even bought in rolls. As a mention on the bridging, I did find it in the code book it is required on joists and rafters that have a height ratio of 6 to 1. In other words either 2X10s or 2X12s need bridging depending on how you use the dimensions. 1X3 or plywood across the tops of all will eliminate that need too. –  Jack Feb 11 at 12:37
    
Thanks for the response. What do you mean about the rafter design being scary? Other than the ceiling joists is there something I can do to beef up the rafters? I've seen a lot about collar ties and purlins. I could add those if that would help strengthen my roof/rafters. –  michael Feb 12 at 4:14

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