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WILL1E
Moderator
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# Posted: 2 Sep 2021 03:55pm
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In case you haven't followed my other threads, goal is to get our 16x32 gambrel roofed cabin shell built and dried in before snow flies. I suspect time and possibly money may not be on my side to get the eave side covered porch done, so i'm trying to make sure i have my bases covered to ensure everything stays dry over winter and minimize how much work i have to do come next year to add the porch and roof on.
The eave wall will be 2x6" studs and 10' tall, balloon framed. Gambrel rafters will be 2x8". Since the tip of the gambrel rafter that touches the top plate is flush with the outside of the wall stud, the plan was to do separate rafter tails so that i could have eave coverage on the non-porch side.
I'm assuming my best option is to do the rafter tails on the porch side and then once i'm ready to build the porch, just design it such that the porch rafters terminate at bend point of the rafter tails and the gambrel rafter? This way all i need to do is remove the materials attached to the rafter tails (steel roofing, sheathing, etc.), cut the rafter tails flush with the cabin side and build the porch roof.
Am i thinking this through correctly?!
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travellerw
Member
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# Posted: 6 Sep 2021 10:58pm
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If you are doing 2X6 walls with 2X8 joists? Then if the tip of that joist lines up with the outside wall, you will have a 2.5 inch overhang on the interior! I know because I just put up my joists and instead put that 2.5 inch overhang on the outside to act as a small soffit vent.
I don't know where you live, but if you haven't started building yet, you may have a hard time even getting the shell up before the snow flies. Especially if you don't have help (and you will need a ton to meet that timeline) or money to hire it.
Another thing I will bring up is the 2X8 Gambrel joists. On a 16ft wide cabin they will weigh about 80 lbs and are SUPER top heavy. They will require 2 8 foot scaffolds and 4 full grown men to move around and install unless you bring in a lift of some sort. (it gets super dicey if there is any wind). A picker truck or boom lift means you could do it with 2 people. Once you have them up, you will also need a plan for the sheathing and roofing material. The roof will be 18 feet tall at the peak (plus any foundation height). Its also VERY steep on lower part. Although it can be done without machinery, its slow going to do safely.
As you may know, I'm now speaking from experience as I'm building essentially the same thing and just spent the long weekend on the joists.
Now, back to your original question. If you do 10 ft walls then its not a big deal. Don't do the tails on the side with the deck and later install the deck roof at 8ft.
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WILL1E
Moderator
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# Posted: 7 Sep 2021 09:04am
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Quoting: travellerw put that 2.5 inch overhang on the outside to act as a small soffit vent.
I'm doing separate rafter tails which will give me the venting i need for the roof. So the question becomes, which way is better structurally?
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travellerw
Member
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# Posted: 7 Sep 2021 01:17pm
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Both are fine structurally. An overhang on the outside is no different than a birdsmouth overhang. Basically that small 2.5 inch overhang only supports the weight of the overhang itself. It literally just needs to support 2.5 inches of roof that is overhanging and any snow load that can accumulate on 2.5 inches of the lower.. So absolutely nothing.
The rest of the roof is supported by the 5.5 inches of joist sitting on the tripled top plate.
Of course a rafter tail will allow for a bigger soffet, but if you only have 2.5 inches in the joist cavity above the insulation that won't matter as that is the choke point for air movement.
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Brettny
Member
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# Posted: 7 Sep 2021 02:32pm
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Why not just do a lower gambrel for this year then next year extend on the lower tails from the top plate.
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WILL1E
Moderator
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# Posted: 7 Sep 2021 02:55pm
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Quoting: Brettny Why not just do a lower gambrel for this year then next year extend on the lower tails from the top plate.
Are you suggesting like travellerw is saying, just have that bottom gambrel rafter extend below the top plate and let it create whatever overhang it naturally creates?
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