nealtw

Bridgeman;
As an engineer yourself you should know better than giving the quick easy answer especially when the ex-ray eyes aren't working. We don't know that the rafter aren't
2x4s joined in the middle.
Keep in mind, the home handyman type often know just enough to be dangerous and will often just take the easy answer and go for it. Adding to the problem is the fact that the answer came from an engineer.
I think it's great for people like Mick to come to a place like this for more info and I beleive it is up to us to give him as much info as posible so he can make his own decisions.

MickChuckB

Ha, don't worry Neal. I'm merely looking to be aimed in the right direction. I wasn't planning on taking information from a message board and pretending I'm some kind of expert. I intend to bring in a pro at some point, but as someone who works somewhat in the construction industry I understand that you can quickly be taken advantage of if you don't know what you're doing or don't have a very specific plan in mind. Here's the rafters before the insulation was put up.

They're spaced 16" and I'm pretty sure they're 2x8s, but that's a complete guess. I'm sitting in my office at the moment so I don't have a quick answer. No clue on the pitch, but 14' - 17' in length seems like a pretty spot-on guess. I hate to hear about the lack of exception for sloped ceilings. I'll have to see if that is the case in Atlanta. I guess it's time to crack the books on local building code. It should be a welcome break from this NFPA 72 that I have been cramming into my head these last few weeks.

MickChuckB

I stopped by my house on lunch and measured the rafters. Much to my dismay, they are 2x6s. It seemed to be a foregone conclusion that they should not be supporting any additional weight so I'm not all that deterred. It seems evident that a beam will need to be installed (assuming any of this will be allowed per code). Luckily, I'm young and single so I've got all the time in the world to tinker and plan. This is the backside of the wall that I intend to move/remove. You can see that there's about a 1-2ft gap opening at the top that goes into the attic.

nealtw

It does look like you have better than 16 ft between the outside wall and the peak. I am really surprized that the added room wall didn't extend to the roof and there are no angle braces. Your knee wall shortens that some BUT I would still be concerned about wind loading and the flex of these 2x6s, If the knee wall is close to the exterior and you get any amount of flexing in the remaining 13 ft, the nails going into the outside wall could be stressed.
Extending the ceiling over to the roof will help but some one that really understands roof structure needs to look it over.

BridgeMan

nealtw--

Sorry, but I'm having trouble understanding your "quick and easy answer" remark. How you read that into my refusal to guess at a load-carrying member's size or span based on pictures is beyond me. Could it be possible you were confusing my comments with those of InspectorD? He mentioned in Post #7 that "this is an easy DIY project" (which is a statement I'd be reluctant to make, as there are too many variables and unknowns that could quickly complicate matters). And to further clarify, any suggestions or answers I make as an engineer are never intended to encourage anyone to do something that's beyond their limits and capabilities.

But getting back on point--Mick, with your rafters only being 2 x 6s, they could well be at their maximum span limits when unsupported at an interior point. American Forest Products span tables for 2 x 6s @ 16" centers shows them only good for a 10'-0" span (assuming Fb of 1800 psi, allowable deflection of L/240, liveload of 50 psf and deadload of 10 psf).

As an aside, I noticed in one of your pix that someone drilled through several adjacent rafters for the purpose of running Romex (electrical wire). Doing so near the center of a span (where its bending moment is greatest) is bad practice, especially when the holes are located in the lower half of the member. In effect, this has turned each 2 x 6 into something considerably weaker. Better to locate holes closer to the neutral axis (center) instead of the tension zone (bottom) of a member, and to make them as small as possible. And better yet to not put any holes in the middle third of any rafter or joist span.

nealtw

Bridgeman: All I am saying is if you go back and look at all the pictures, do you see a problem with span length, bracing and do you see a bearing wall. I was that that guy with a hammer and saw with an attitude of "lets getter done" and I know the damage that can be done.
Does the follwing statement help some one understand all the problems he may face?
"You may not have nearly as large a problem as you think. Particularly if there are other rooms in the upper level with functional wall/ceiling framing similar to what you'd like to do in the unfinished rooms"