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Discussion Starter #1
I am designing a house. Are there any rules to the depth of rafter seat cuts. I have 2x12 rafters on a 2x6 pony wall. Roof is 12:12 pitch.
 

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General Contractor
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Typical heel height for a 2x12 @ 12/12 is 10-7/16" - that gives you 5.5 for the seat cut which allows to run the plywood over the ends of the rafters. If you have soffits that will cover the ends of rafters then don't worry about running the plywood up - you'll already have blocking between rafters anyway.
cdac's solution will work also - this is just the way my truss manufacturer and I have always done it. Where we have truss's and stick framed coming together - they will then always match.
 

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Nice work cdac.. drawings always help :)
I also use the same dimensions for rafters too.. mostly because I'll cut down the 2x12 to a 2x6 for an exposed soffit. Essentially from cdac's drawing the depth of the rafter to the exterior side of the wall is 5.5". Do it this way mostly out of habit than anything else - of course it depends on what the design warrants also :) .
 

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Discussion Starter #6
cdac said:
Hatchet's description would be the way to go if you go with trusses for nice looking eves. here is a general cross section sketch, hope this helps.
Thank you for the advice, I sincerely appreciate it. I have a degree in mechanical engineering technology, this is my first attempt at designing a house. This is not my expertise, but I have a strong grasp on forces at play. It helps immensely to speak with the pros that actually do the building! Does this depth weaken the load capacity of the rafter. Is it necessary to seat the rafter at the full width of the 2x6?
 
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wwknight2 said:
Does this depth weaken the load capacity of the rafter.
I suppose if you will be suspending several M-1 Abrahms tanks from your eves and jumping up and down on top of them you will encounter problems, otherwise no.

wwknight2 said:
Is it necessary to seat the rafter at the full width of the 2x6?
Yes, Why wouldn't you? I hope you are not overlooking collar ties on this 12/12 2x12 framed behemoth.
 

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Design Build
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I have mostly stick framed roofs in Houston and strange places in TN. We used 2x6 rafters or maybe 2x8 rafters. What's with y'all using 2x12 rafters when stick framing, and yet a 2x4 truss is cool. If its for insulation in a cathedral roof - that's okay...but if not - is snow THAT heavy?
 

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The Duke
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is snow THAT heavy?
Very! You must of missed the 12" or so of snow we had in the Seattle are awhile back where it caused massive, massive damage. Heavy, wet snow, like when it snows at 31 or 32 degrees and get a foot on the roof and you have yourself a problem...especially if it ices over.

Seattle at the time had a 25# live load and they built according to it. A friend of mine was taking engineering class at UW. He decided to hop up onto his roof and get a cubic foot of snow. He had 80,000 lbs of snow on his roof he said.
 
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