Valley Cuts When Their Are Two Diff Pitches - Building & Construction - DIY Chatroom Home Improvement Forum

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02-06-2012, 04:37 AM   #1
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## valley cuts when their are two diff pitches

what does the valley cut on when theirs 12/12 pitch that meet 12/16

02-06-2012, 07:23 AM   #2
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That's called a bastard because they're difficult to figure.
Bevel 40° (12/12 hv)(scribe) and miter (?) 12/16 h/v(saw table).

Last edited by titanoman; 02-06-2012 at 07:45 AM.

02-06-2012, 10:01 AM   #4
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Quote:
 Originally Posted by WillK Isn't roof pitch usually rise/run and the rise is stated in terms of 12" of run, so 12/16 could be described as 9/12? So I'm an engineer, I can do geometry, let's see if I can walk ya through this. Starting with your 9/12 pitch, if you start from a point at the top, then come down 9 then across 12, then you come across perpindicular to that by 9 (since your 12/12 pitch roof would have come down 9, it comes across 9). This gets you to the point at the top of your valley. Taking your two legs where you came across, using pythagorean theorm 9^2+12^2=x^2. X=15. This is the amount that your valley comes across horizontally after 9 of rise. So that would figure into how your ends will be cut. Viewing from the top, to get your bevel angle, you're going across in the direction the 9/12 roof slopes by 12 and in the direction the 12/12 roof slopes by 9. So your angle should equal inverse tangent (9/12) = 36.9 degrees.
I rounded it off to 40°.

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