Dining room addition with Porch.

[doitmyselfer]

I'm planning to add a new dining room (hip roof). I did an office addition last year, but this time I'd like to add a vaulted (or stepped) ceiling and a covered porch. This seems to make things a little trickier.

I'm not sure how to move the joists up the foot or 2 for the vault. With the office, they just rested on the new walls (running parallel to the existing house). Is it OK to just fasten the joist to the rafters (almost like a collar tie) without resting on the walls? I've read somewhere that it changes the allowable rafter/joist span? And what about under the hip, once you lift the joists. In the office, I just added perpendicular joists when the roof got too low. (4/12 pitch roof). Will that work? It seems like a strange setup.

Also, the porch seems to compound things. I assume the outside edge of the porch is the load bearing wall, and the partition between the room and porch is non-bearing? Is it better to make both walls bearing to reduce the lumber size? Total size is 12x21 (long side against the house), (12x15 room, 12x6 porch) and I was planning to run the joists parallel to the existing house. What about perpendicular instead? Is it more difficult to tie into the house running them perpendicular? If I run joists perpendicular, do I tie into the existing house rafters?

I've thought about scrapping the stepped ceiling and just using 10' foot walls/ceilings on the addition, but I'm not sure how to tie into the 8' foot walls of the existing house. Do I just cut the eaves and extend the wall up 2'? This method would seem to simplify the joists. But does it complicate something else that I don't see? I'd have to make the new eaves 6' wide to match the height on the existing house, so I guess that's out. Would there be problems (other than aestetic) in leaving the widths of the eaves narrow and higher than the rest of the house?

This was a bit of a rambling post, but any ideas/suggestions are appreciated.


Thanks.

[Rich]

Let me ponder this for a bit. Maybe do a drawing with what you've told me in your post. I'll see what I can come up with for you.

Off the top of my head I think 10' walls would be the best thing but let me look at it to make sure.

[doitmyselfer]

Thanks. I have the floorplan (no roof/ceiling info) in 3D home architect, (can export to DXF or WMF), if that would be of any help.

[Rich]

You bet.. export as DXF and email it to me. I'll see if I can get something back in a day or so from getting it. That'll save some time.

[Rich]

Ok. I'm going to answer this in parts as I look at each piece. In regards to the eaves - I think it would look fine if you left them higher if you go with the 10' walls.

So from here would you like a framing plan or something else? For everyone elses benefit doitmyselfer has sent me a dxf of the floor plan. On the existing roof do the trusses / rafters span from the dining room side to the garage side? I am going to assume that - because it's the shorter span. Also - what is the overhang and is it a boxed eave or a straight overhang?
I'll do it with the 10' walls and without cutting into the existing roof, if that works for you.

[doitmyselfer]

Your assumption is correct. The majority of the house is hip roof, so rafters are perpendicular to each side (not trussed). It is a boxed eave. (1 foot finished width). I just did a run up to the attic and it appears that the joists for the kitchen are running parallel to the outside wall. Not sure if that matters. I also should mention that the living room is a cathedral ceiling, (high point running from the front of the house to the kitchen wall). so if that creates any difficulty, I can just shorten the addition to match the southern exterior wall to the interior kitchen wall.

I don't know what I need exactly, I guess a framing plan would be very helpful. This seems to be running away from me quickly. If I had realized how involved a little extra height was going to be, I might not have ventured down this road. Of course, better now than after I've gotten the new walls up and half the old roof off. :lol:

[Rich]

Ok.. I was almost done when you posted your message of 1' boxed eaves (I already had a 2' overhang). I wasn't sure how the rest of the roof was either - but just made an assumption of all hips. Anyway here's what I came up with. If you want to make some changes just let me know. Or I can export (DXF) and send it back to you.
Plan & Elevations (http://www.construction-resource.com/images/temp/dimyself.jpg)

[doitmyselfer]

This looks how I envisoned it. So how does it tie in at the existing house?

[Rich]

Overframing. You would have 2x lumber running from the peak down the roof at a 45° angle to where it would meet the overhang. Then the rafters get cut to that. The ridgebeam goes from the hip peak back to meet the existing roof. You can use the rafter calculator (http://www.construction-resource.com/roof_frame.php) on this site to figure the angles to cut for jack rafters. It also gives lengths etc.

[doitmyselfer]

I'm think I'm OK on the roof and rafters. I was really asking about the ceiling and joists. Do I just add 2' to the existing 8' wall (triim the eaves to the wall and add an extension above?) and run the joists on top? Is it ok to have the original house common rafters running "inside" this extension, or should I build the extension above/on the existing roof sheathing? Is it better to run the joists perpendicular to the house or parallel? Is there any advantage to running them parallel with two sets of joists (no non-bearing wall)? Thanks for all your help so far, I hope I'm not being too dense.

[Rich]

Sorry about that.
Starting with the floor joists. Either way you want to frame them is just fine. Some things to think about - if you frame them parallel with the wall of the house you can span from concrete to concrete. This essentially means that you won't need to expansion anchor or lag bolt a ledger onto the existing wall / foundation. But is also may mean that you need to put in a pony wall below the floor to help support the span. This isn't much of a problem and it doesn't need to be perfect.
As far as the ceiling goes I would frame up the existing wall (inside of the room) to the underside of the ceiling. And on the sides you could frame new walls right on top of the sheathing. Although you may want to add in blocking between the existing rafters under the sheathing to help carry the additional weight. If you end up right on top of a rafter I would suggest doubling up the existing rafter. Now you can do whatever you want as far as the ceiling goes. Either apply drywall right to the rafters or put in ceiling joists to frame out for a coffered ceiling. If you end up going with a coffered ceiling (not vaulted) I would suggest scrapping everything I've just told you and go with trusses..haha. It'll be about 3 times faster and they'll be engineered to carry any and all loads present.
I hope that answers your questions.. if not "Try, try again". Maybe I'm being dense too. :D

[doitmyselfer]

I keep making this harder than need be. I forgot to tell you that this would all be on a concrete slab foundation, no floor joists. So, I was only asking about the ceiling joists. If that changes any of your recommendations, let me know. I think I got the gist of it, though. Thanks again.

[Rich]

Oh.. umm.. Just disregard the portion of the post below on floor joists. The rest still applies.. that is if you understood my rambling.