Framing a Shed Dormer into a cathedral ceiling
I have a shed roofed kitchen addition with a cathedral ceiling on the side of my house. Currently it has two outdated skylights and a roof that is in bad need of replacement. Since we have to take the roof down to the rafters anyways (asphault shingles over cedar shingles over lathe, no sheathing) I’m considering adding a shed dormer to the roof with a row of windows rather than replacing the skylights. Its a south facing wall and I think the windows will let in more light, and stay cleaner than the skylights. The windows would not be that tall, maybe 1.5-2′ high awning style windows. Might even spring for electric motors to open and close. My question is how to frame the dormer properly? I can find plenty of reference for shed dormers whose cheek walls extendend down to the floor. However, I can’t find anything that shows how I would frame in the walls in a cathedral type ceiling. The dormer wall with the windows will be situated over the existing exterior wall of the house for support. However, for asthetic reasons, the cheek walls of the dormer will not be over the existing exterior walls on either side of the kitchen – just looks a lot better with the dormer not extending the entire length of the addition. Any advice on where to look for framing plans, or specific instruction would be much appreciated. To help understand what I’m talking about, I’m attaching a pic that shows before and after mocked up with photoshop. Thanks!
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The cheek walls will sit on rafters the rafters. You'll have to double up the rafters under cheek walls. Sounds like an old house with old lumber; the rafter work will be quite interesting.
How would that work if the rafters that are part of the dormer are supported by the dormer's wall with the windows, and the rafters that are part of the roof on either side of the dormer have to sit on the outside of that wall? Not sure if that makes sense, so I did a really quick drawing of what I mean. See attached.
The end rafter sits on the cheek wall and is trimmed to match the roof line.
The fly rafter is similar but will need blocking underneath at the top end and is attached to a 2x subfacia.
Be sure that when you frame for your window wall to remember the height of the dbl top plate that will connect the widow wall to the cheek walls.
Remember your flashing, will be easier to flash it right before you set the flyrafter. Flyrafter will need a bit of flahsing too at the top.
Your drawing shows dbl jack studs (or trimmers) iunder the header, you may not need them depending ont he span.
fly rafter support
but you're probably in snow country so the fly rafter will need soem mroe support... nothc 2x4 lookouts into the end rafter that sits onthe cheek wall. Run the lookouts between the fly and the 1st whole rafter. you can probably get by with 24"oc spacing on the lookouts.
Yes, in NJ - so snow is a factor. The rest of the house's gable ends don't use a fly rafter, so is it necessary, or just asthetic? You can see in that original picture I posted. So maybe something like this? I added the top plate on the dormer window wall, as well as a ledger to attach short extensions to continue the main roof below the dormer. I also read about making birds mouth cuts in the dormer rafters to help get the soffit closer to the tops of the windows and to help retain as much slope as possible. I'd probably use a hanger on the inside to help with that support. Just curious if you think its looking proper?
roof pitch?
and the next quesiton is how flat wil the dormer roof be? Get it below 3:12 and it calls for special roofing procedures that I'm not all that familiar with. You'll have to do your homework and/or find a competent roofer.
I've done the measurements and I'll still be at least 3:12, so should be ok on that front. I went back and found the Fine Homebuilding article that I remembered reading about cutting the birds mouth's deeper. I attached below. It says exactly what you just did about losing the dbl top plate and using the header as the first of the two. Can you see what you think about the birds mouth as they explained it?
Also meant to say that part of the reason it was showing too many top plates was that I had put in some blocking so that the end studs and top plate of the cheek wall would be supporting the dbl top plate of the window wall. My birds mouth was so deep that the dbl plate didnt get below the bottom of the rafter. So that last angled end you see is just blocking to get it all in contact. May still need to do something like that if I drop it down to a single plate on the window wall.
if it helps you gain
I haven't seen that drwg before (dropped the sricpt to the mag) but it would work if it's necessary. I would avoid it if I could but if you need the few inches it gains to keep your roof =>3:12 or into standard sized windows the extra time/labor could pay off.
I think that drwg from the mag would work good for lower ceilings and/or incredible views. But this is for a window bank that is way above eye level, right? Consider the view it will gain you beofre you commit to all those cuts mulitplied by every rafter and then a few chunks of the tails breaking off. Then you got fill every hole in those hangers, not a bad deal with a pos placement gun or palm nailer but by hand they're a pain.
Don't go crazy filling all the gaps in your rough framing, it's not furniture.
post updates
You're welcome. Let us knwo how it develops and psot some pictures if you forward with it.